Updated on 2024/10/08

写真a

 
KOYAMA Keiichi
 
Organization
Research Field in Science, Science and Engineering Area Graduate School of Science and Engineering (Science) Department of Science Physics and Astronomy Program Professor
Research Field in Science, Science and Engineering Area Graduate School of Science and Engineering (Science)
Research Field in Cooperation, Integrated Arts and Sciences Area Center for Advanced Science Research and Promotion Research Support Center, Institute for Research Promotion
Title
Professor
Profile
High magnetic field, materials science under high magnetic fields

Degree

  • 博士(学術) ( 1997.3   広島大学 )

Research Interests

  • 強磁場物質科学

  • 相転移制御

  • 機能性材料

  • 高圧力

  • materials science

  • high magnetic field

  • 磁性材料

  • 磁性

  • 物性

  • 強磁場

  • 高圧

Research Areas

  • Nanotechnology/Materials / Metallic material properties

  • Nanotechnology/Materials / Structural materials and functional materials

  • Nanotechnology/Materials / Metallic material properties  / 磁性

Education

  • Hiroshima University

    - 1997.3

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    Country: Japan

  • Hiroshima University   Graduate School of Biosphere Science

    1994.4 - 1997.3

  • Ehime University

    - 1994.3

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    Country: Japan

  • 愛媛大学大学院   理学研究科   物理学専攻

    1992.4 - 1994

  • Ehime University

    1988.4 - 1992.3

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    Country: Japan

  • Ehime University   Faculty of Science

    1989.4 - 1992.3

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Research History

  • Kagoshima University   Research Field in Integrated Studies, Integrated Arts and Sciences Area National Science Center for Research and Education

    2020.4 - 2022.3

  • Kagoshima University

    2023.4

  • Kagoshima University

    2022.4

  • Kagoshima University   Research Field in Science, Science and Engineering Area Graduate School of Science and Engineering (Science) Department of Science Physics and Astronomy Program   Professor

    2020.4

  • Kagoshima University   Research Field in Science, Science and Engineering Area Graduate School of Science and Engineering (Science)

    2019.4 - 2020.3

  • Kagoshima University   Research Field in Science, Science and Engineering Area Graduate School of Science and Engineering (Science)

    2017.4

  • Kagoshima University

    2017.4 - 2023.3

  • Kagoshima University   Research Field in General Educathion, Integrated Arts and Sciences Area Center for Research and Development in Higher Education, Institute for Comprehensive Education

    2017.4 - 2019.3

  •   科学研究費委員会専門委員

    2016.12 - 2018.3

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    Country:Japan

  • Kagoshima University   Research Field in Science, Science and Engineering Area Graduate School of Science and Engineering (Science)

    2016.4 - 2017.3

  • 独立行政法人大学入試センター   試験問題作成者

    2014.4 - 2016.3

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    Country:Japan

  • Kagoshima University   Professor

    2010.1

  • Kagoshima University   Research Field in Science, Science and Engineering Area Graduate School of Science and Engineering (Science) Physics and Astronomy Course   Professor

    2010.1 - 2020.3

  • Tohoku University   Institute for Materials Research, High Field Laboratory for Superconducting Materials   Associate Professor

    2007.4 - 2009.12

  • Tohoku University   Associate Professor

    2001.12 - 2009.12

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    Country:Japan

  • Tohoku University   Institute for Materials Research, High Field Laboratory for Superconducting Materials   Associate Professor (as old post name)

    2001.12 - 2007.3

  • Tohoku University   Research Assistant

    1998.4 - 2001.11

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    Country:Japan

  • Tohoku University   Magnetism, Institute for Materials Research   Research Assistant

    1998.4 - 2001.11

  • The University of Tokyo   Part-time researcher for university or other academic organization

    1997.4 - 1998.3

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    Country:Japan

  • The University of Tokyo   The Institute for Solid State Physics

    1997.4 - 1998.3

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Professional Memberships

  • 日本鉄鋼協会

    2015.10

  • 日本磁気科学会

    2015.10

  • 日本金属学会

    2015.10

  • 日本物理学会

    2015.10

  • 研究費配分に関する教育研究環境検討委員会委員

    2015.4

  • 日本磁気科学会理事

    2015.1 - 2017.12

  • 東北大学金属材料研究所附属強磁場超伝導材料研究センター共同利用委員会

    2013.4 - 2016.3

  • 日本金属学会会報編集委員

    2013.3 - 2015.3

  • 日本磁気科学会役員

    2012.12 - 2014.11

  • 応用物理学会

    2011.5 - 2015.12

  • 東北大学金属材料研究所附属強磁場超伝導材料研究センター共同利用委員会

    2010.4 - 2012.3

  • 東北大学金属材料研究所附属強磁場超伝導材料研究センター専門委員会

    2002.4 - 2009.12

  • 東北大学金属材料研究所附属強磁場超伝導材料研究センター運営委員会

    2002.4 - 2009.12

  • 日本物理学会

  • 日本鉄鋼協会

  • 日本金属学会

  • 日本磁気科学会

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Committee Memberships

  • 日本磁気科学会   理事(中四国九州支部会長)  

    2019   

  • 独立行政法人日本学術振興会   科学研究費助成事業審査 意見書作成者  

    2018   

  • 研究費配分に関する教育研究環境検討委員会委員   委員  

    2015.4   

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    Committee type:Other

    一般社団法人日本物理学会

  • 日本磁気科学会理事   理事(中国・四国・九州支部長)  

    2015.1 - 2017.12   

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    Committee type:Other

    日本磁気科学会

  • 東京大学物性研究所   共同利用施設委員会 委員  

    2014 - 2016   

  • 独立行政法人大学入試センター   教科科目第一委員会 委員  

    2014 - 2016   

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    Committee type:Government

  • 強磁場フォーラム幹事   幹事  

    2013.4 - 2016.3   

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    Committee type:Other

    強磁場フォーラム

  • 東北大学金属材料研究所附属強磁場超伝導材料研究センター共同利用委員会   東北大学金属材料研究所附属強磁場超伝導材料研究センター共同利用委員会委員  

    2013.4 - 2016.3   

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    Committee type:Other

    東北大学金属材料研究所

  • 日本金属学会   学会誌編集委員  

    2013.3   

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    Committee type:Other

    日本金属学会

  • 強磁場フォーラム   幹事  

    2013 - 2016   

  • 東北大学金属材料研究所   共同利用委員会委員および採択専門委員会委員  

    2010 - 2016   

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Qualification acquired

  • 有機溶剤作業主任者技能講習修了証

  • Hang Up and Remove Work Skill Person

  • Floor Above Operation Type Crane Skilled Person

  • X-ray Work Chief Person

  • Person in Charge of High-pressure Gas Production Security (chemical machinery and frozen machine)

  • High School Teacher Specialization License

  • First Kind of High School Teacher License

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Papers

  • Keiichi Koyama, Yoshifuru Mitsui, Saki Imatsuji, Akari Onaka, Ryota Kobayashi, Masahira Onoue, Reisho Onodera .  Study of heat treatment effect on magnetic properties of MnFeGe using <sup>57</sup>Fe Mössbauer spectroscopy .  Interactions245 ( 1 )   2024.12

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

    X-ray powder diffraction, magnetization, and 57Fe Mössbauer spectroscopy measurements were performed to investigate the effects of heat treatment on the magnetic properties of MnFeGe with hexagonal Ni2In-type structure. The samples were annealed at 1173 K for 24 h, as a solution treatment (ST), and then aged at 1073 K (AG-1073 K), 973 K (AG-973 K) and 773 K (AG-773 K). Curie temperature was the highest at AG-1073 K (201 K), and the lowest at AG-773 K (169 K). In ST and AG-1073 K, Mössbauer spectrum was represented by three subspectra. In AG-1073 K, 19% of the Fe atoms occupied 2a-site and 71% of the Fe atoms occupied 2d-site. The hyperfine fields of 2a- and 2d-sites at 15 K were 20.3 T and 9.99 T, respectively. Approximately 10% of the iron atoms contributed to the subspectrum of nonmagnetic phase. On the other hand, to represent the spectra obtained at 15 K for samples annealed at lower temperatures (AG-973 K and AG-773 K), an additional subspectrum with the hyperfine field of 21.6–22.0 T was required, which was due to the ferromagnetic impurity phase. The obtained results showed that as the aging temperature decreased, Fe occupying the 2a-site with a large hyperfine field decreased, resulting in a decrease in the macroscopic magnetic properties of MnFeGe.

    DOI: 10.1007/s10751-024-01951-9

    Scopus

  • Kobayashi R., Mitsui Y., Yoshizaki Y., Takahashi K., Takamine K., Koyama K. .  Controlling the growth of yeast by culturing in high magnetic fields .  Journal of Magnetism and Magnetic Materials586   2023.11Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Journal of Magnetism and Magnetic Materials  

    The effect of static magnetic fields up to a strength of 15 T on the growth of three types of yeast which were all classified as Saccharomyces cerevisiae was studied. The growth rate of the yeasts was suppressed by applying a magnetic field. The degree of suppression depended on the type of yeast. The reduction in the numbers of yeast cells was due to growth suppression, not sterilization. Among the three types of Saccharomyces cerevisiae, the degree of suppression on the growth of two yeasts was strongest in a magnetic field at 8 T with different suppression degree of 19% and 12% for a culture time of 24 h. Growth of the other yeast most suppressed by 10% at a magnetic field of around 4 T. Therefore, the yeasts have their characteristic magnetic field sensitivity on the growth. The results were discussed using a model based on the competition between yeast osmotic pressure changes by magnetic field and magnetic forces induced by magnetic field gradient. In low magnetic field regions, change of the osmotic pressure shrink the yeast cell and reduce the contact frequency between yeast cells and glucose-based ions. In higher magnetic field regions, effect of magnetic force become apparent, and recover the growth rate of the yeast. It suggested that the selective growth of yeast can be expected by in-magnetic-field culturing.

    DOI: 10.1016/j.jmmm.2023.171193

    Scopus

  • Takaoka Taisei, Mitsui Yoshifuru, Koyama Keiichi, Fujii Shinpei .  Site Selectivity and Structural Stabilization in Cu-Doped or Fe-Doped MnCoGe .  MATERIALS TRANSACTIONS64 ( 9 ) 2109 - 2112   2023.9Reviewed

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    Language:English   Publisher:The Japan Institute of Metals and Materials  

    <p>We performed first-principles calculations to investigate the effect of Cu or Fe partial substitution in MnCoGe on the stabilization of the hexagonal structure. In the case of Cu partial substitution at <i>x</i> = 0.125, a substitution for one site is more effective than that for both sites. In the case of Fe partial substitution at <i>x</i> = 0.125, there is no difference between two types of substitution for both sites and the Mn site. The result of Fe partial substitution at <i>x</i> = 0.25 indicates that Fe partial substitution for both sites is more effective than that for the Mn or the Co site.</p>

    DOI: 10.2320/matertrans.mt-mg2022011

    Scopus

  • Nakamoto Kota, Mitsui Yoshifuru, Kobayashi Ryota, Koyama Keiichi .  In-Magnetic-Field Heat Treatment Effects on Phase Growth of Mn–Bi–Sn Composite .  MATERIALS TRANSACTIONS64 ( 9 ) 2113 - 2117   2023.9Reviewed

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    Language:English   Publisher:The Japan Institute of Metals and Materials  

    <p>To investigate the magnetic field effect on the synthesis reaction and phase growth in a Mn–Bi–Sn composite pellet, in-field heat treatments were performed in 5 T at 573 K for 1 to 48 hours. X-ray diffraction measurements and electron probe micro analysis revealed that MnBi phase did not appear but Mn<sub>3</sub>Sn, Mn<sub>3</sub>Sn<sub>2</sub> and MnSn<sub>2</sub> phases were detected in the pellet. In zero-field heat treatment, the phase fraction of Mn<sub>3</sub>Sn<sub>2</sub> increased and that of MnSn<sub>2</sub> decreased as the heat treatment time increased. In contrast, no significant change in the phase fractions of Mn<sub>3</sub>Sn<sub>2</sub> and MnSn<sub>2</sub> phase was observed in 5 T even if the heat treatment time was increased to 48 h. The obtained results suggested that the application of magnetic field suppressed the diffusion of Mn atoms between Mn–Sn phases.</p>

    DOI: 10.2320/matertrans.mt-mg2022014

    Scopus

  • Masahira ONOUE, Yoshifuru MITSUI, Saki IMATSUJI, Ryota KOBAYASHI, Reisho ONODERA, Keiichi KOYAMA .  Magnetic Properties of MnFeGe Probed Using 57Fe Mössbauer-spectroscopy .    38 - 011139   2023.5Magnetic Properties of MnFeGe Probed Using 57Fe Mössbauer-spectroscopyReviewed

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    Language:English   Publishing type:Research paper (international conference proceedings)  

    DOI: 10.7566/JPSCP.38.011139

  • Yoshifuru MITSUI, Hideto TANAKA, Masahira ONOUE, Moriharu NAGANO, Ryota KOBAYASHI, Rie Y. UMETSU, Keiichi KOYAMA .  Magnetic and Hyperfine Properties of FeZnSb .  JPS Conference Proceedings38   011138   2023.5Magnetic and Hyperfine Properties of FeZnSbReviewed

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    Language:English   Publishing type:Research paper (international conference proceedings)  

    DOI: 10.7566/JPSCP.38.011138

  • Akari Onaka, Masahira Onoue, Reisho Onodera, Yoshifuru Mitsui, Keiichi Koyama .  Magnetic and structural properties of Fe-substituted MnCoGe with Ni2In-type structure .  Journal of Magnetism and Magnetic Materials563   170000 - 170000   2022.12Reviewed

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Elsevier BV  

    DOI: 10.1016/j.jmmm.2022.170000

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  • Junki Takahashi, Yoshifuru Mitsui, Masahira Onoue, Ryota Kobayashi, Keiichi Koyama .  Nitridation kinetics of Sm<inf>2</inf>Fe<inf>17</inf> probed using Mössbauer spectroscopy .  Journal of Magnetism and Magnetic Materials554   2022.7Reviewed

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

    In this study, the Sm2Fe17 powder was subjected to nitridation at 743 K under N2 pressures of 0.05 and 0.1 MPa to investigate the growth kinetics of Sm–Fe–N. Two-phase growth of the fully nitride (FN) Sm2Fe17N3 phase and the nitrogen-poor (NP) Sm2Fe17Nx phase (0 < x < 3; x denotes the nitrogen content) was observed using 57Fe Mössbauer spectroscopy. Although the x value was greater at 0.05 MPa than at 0.1 MPa in the early stage of nitridation, the opposite trend was observed in the later stage. At a nitrogenation time of 24 h, nitridation was nearly complete at 0.1 MPa, while x tended to saturate and did not reach 3 at 0.05 MPa. The nitridation process was discussed based on two simultaneous growth processes: (i) the diffusion of the nitrogen atom in the NP phase and (ii) the nucleation and growth of the FN phase. A process combining N2 pressure and nitrogenation, which facilitated nitrogenation under low N2 pressure and high N2 pressure at the beginning and end of the nitridation process, respectively, achieved faster nitridation than process with a single N2 pressure.

    DOI: 10.1016/j.jmmm.2022.169295

    Scopus

  • Fujii S., Mitsui Y., Koyama K. .  Ab initio Study of Atomic-disorder Effect on Electronic and Magnetic Properties of CrAGe .  Journal of the Physical Society of Japan91 ( 6 )   2022.6Reviewed

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    Language:English   Publisher:Journal of the Physical Society of Japan  

    First-principles calculations show that the atomic disorder between Al and Ge does not destroy the half-metallic character of CrAlGe, and that its unique character is, however, destroyed by the swap between Cr and Al (or Ge). Our analysis of the X-ray diffraction patterns of CrAlGe indicates the existence of this swap disorder.

    DOI: 10.7566/JPSJ.91.064706

    Scopus

  • Ryota Kobayashi, Yoshifuru Mitsui, Rie Y. Umetsu, Kohki Takahashi, Keiichi Koyama .  Acceleration of B2/L2<inf>1</inf> order-disorder transformation in Ni<inf>2</inf>MnAl Heusler alloys by in-magnetic-field annealing .  Journal of Magnetism and Magnetic Materials547   2022.4Reviewed

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

    Ferromagnetic L21 phase of Ni2MnAl with high order degree is difficult to synthesize because of low L21/B2 order-disorder transformation temperature. It is found that magnetic field accelerated the transformation from the antiferromagnetic disordered B2 to ordered L21 phase. Magnetization increased by in-magnetic-field annealing at 673 K, which indicated the acceleration of the ordering to L21 phase. Magnetic field effects on the B2/L21 order-disorder transformation were discussed based on magnetic-field-induced change of transformation temperature, enhancement of degree of order at annealing temperature, and reduction of critical radius of L21 nuclei. Growth kinetics of L21 phase were evaluated by Johnson-Mehl-Avrami equation, which indicated that 15-T annealing accelerated the growth of L21 phase 5.7 times faster than zero-field annealing. Our results showed that magnetic field can contribute to shortening the annealing time for synthesis of ferromagnetic L21-Ni2MnAl alloy.

    DOI: 10.1016/j.jmmm.2021.168908

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  • Mitsui Yoshifuru, Onoue Masahira, Kobayashi Ryota, Sato Kaori, Kuzuhara Shunsuke, Ito Wataru, Takahashi Kohki, Koyama Keiichi .  High Magnetic Field Effects on Cu-precipitation Behavior of Fe-1mass%Cu at 773 K .  ISIJ International62 ( 3 ) 413 - 417   2022.3Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:The Iron and Steel Institute of Japan  

    <p>Tramp elements in steel, such as Cu and Sn, cannot be removed by acid treatment. Since these elements condense by repeating recycling process, leading to deterioration of strength. Therefore, the methods for avoiding condensation or removing tramp elements are required. In this study, in-magnetic-field annealing process was focused on because magnetic field is effective for diffusion, phase transformation, phase diagram and precipitation. In-magnetic-field annealing of Fe-1mass%Cu at 773 K was performed in 5 and 10 T for investigating precipitation behavior of supersaturated Cu. From microstructural observation, precipitation of Cu-rich phase in Fe-matrix, and magnetic field effect on itself were not observed clearly. Increase of the hyperfine field was detected for the samples annealed at 5 T by Mössbauer spectroscopy, indicating the enhancement of the Cu-precipitation. On the contrary, hyperfine field for 10T-annealed sample was slightly smaller than that for 0 T. Therefore, in-field annealing effect on Cu-precipitation became unclear at 10 T. These magnetic field effects were discussed in the viewpoints of the change of Cu–Fe phase diagram and the atomic diffusion under magnetic field. Difference of the magnetic field effects on precipitation between 5 T and 10 T is explained by the competition between the enhancement of the driving force of the precipitation and suppression of the atomic diffusion. The obtained results indicated that there is optimized magnetic field intensity for controlling Cu-precipitation.</p>

    DOI: 10.2355/isijinternational.isijint-2021-404

    Scopus

  • Hiroi M. .  High magnetic field properties in Ru2-xFexCrSi with antiferromagnetic and spin-glass states .  Physical Review B103 ( 9 )   2021.3Reviewed

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    Language:English   Publisher:Physical Review B  

    DOI: 10.1103/PhysRevB.103.094428

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  • Kobayashi Ryota, Mitsui Yoshifuru, Umetsu Rie Y., Mizuguchi Masaki, Koyama Keiichi .  Synthesis of Ferromagnetic τ-Mn–Al–C by Reactive Sintering .  MATERIALS TRANSACTIONS62 ( 1 ) 130 - 134   2021Reviewed

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    Language:English   Publisher:公益社団法人 日本金属学会  

    <p>Ferromagnetic Mn–Al–C (τ-phase) can be synthesized by a single-route conventional reactive sintering method. The maximum magnetization and coercivity were 75.8 Am<sup>2</sup>/kg and 57 mT, respectively. The τ-phase fraction was evaluated to be 81 mass% for Mn<sub>55</sub>Al<sub>45</sub>C<sub>2</sub> annealed at 1273 K. The τ-phase of Mn<sub>55</sub>Al<sub>45</sub>C<sub>2</sub> can be synthesized at an annealing temperature from 873 to 1273 K, whereas that of Mn<sub>55</sub>Al<sub>45</sub> cannot be synthesized. It was indicated that the phase stability of the hcp-phase (ε-phase) was improved by adding carbon, resulting in an ε–τ transformation.</p>

    DOI: 10.2320/matertrans.MT-M2020166

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  • Kobayashi Ryota, Takaki Akio, Mitsui Yoshifuru, Umetsu Rie Y., Takahashi Kohki, Mizuguchi Masaki, Koyama Keiichi .  Dual Acceleration of ε-τ Transformation in Mn–Al Induced by Zn-Addition and In-Magnetic-Field Annealing .  MATERIALS TRANSACTIONS62 ( 1 ) 124 - 129   2021Reviewed

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    Language:English   Publisher:公益社団法人 日本金属学会  

    <p>Combined accelerating effects of ε–τ phase transformation by in-magnetic-field annealing and Zn-addition were investigated for Mn<sub>53</sub>Zn<sub>2</sub>Al<sub>45</sub> in magnetic fields up to 15 T. The in-field annealing for Zn-added sample accelerated the ε–τ transformation 16 times faster than Mn<sub>55</sub>Al<sub>45</sub> at annealing temperature of 623 K. The reduction of magnetization after finishing ε–τ transformation was also more rapid than that of Mn<sub>55</sub>Al<sub>45</sub>. However, magnetic-field-induced acceleration of ε–τ phase transformation and suppression of precipitation of β-phase were observed for Zn-added alloy Mn<sub>53</sub>Zn<sub>2</sub>Al<sub>45</sub> annealed at 573 K. The obtained results suggested that the β-phase stabilized against both τ- and ε-phases by Zn-addition. Therefore, although the ε–τ transformation was efficiently accelerated by in-field annealing of Mn<sub>53</sub>Zn<sub>2</sub>Al<sub>45</sub>, more precisely control of annealing time is required for obtaining high fraction of ferromagnetic τ-phase.</p>

    DOI: 10.2320/matertrans.MT-M2020235

    Scopus

  • Yumi Watanabe, Ryota Kobayashi, Yoshifuru Mitsui, Rie Y. Umetsu, Keiichi Koyama .  Magnetic-field-induced selective retardation of reaction in Mn/Ga diffusion couple .  Journal of Alloys and Compounds887   161310 - 161310   2021Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Elsevier BV  

    DOI: 10.1016/j.jallcom.2021.161310

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  • Shun Nakagawa, Yoshifuru Mitsui, Ryota Kobayashi, Rie Y. Umetsu, Kohki Takahashi, Keiichi Koyama .  Magnetic-field-induced decomposition in Cu2MnAl Heusler alloys .  Journal of Magnetism and Magnetic Materials540   168411 - 168411   2021Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Elsevier BV  

    DOI: 10.1016/j.jmmm.2021.168411

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  • Y. Mitsui, Y. Takanaga, R. Kobayashi, K. Koyama .  Effect of carbon addition on the phase stability of hcp-Mn-Al .  Physics B595   412379   2020.10Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: https://doi.org/10.1016/j.physb.2020.412379

    Other Link: https://www.sciencedirect.com/science/article/pii/S0921452620303884

  • M Onoue, R Kobayashi, Y Mitsui, RY Umetsu, Y Uwatoko, K Koyama .  Magnetic field-induced nitridation of Sm2Fe17 .  J. Alloys Comp.835   155193   2020.9Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: https://doi.org/10.1016/j.jallcom.2020.155193

    Other Link: https://www.sciencedirect.com/science/article/pii/S0925838820315565?via%3Dihub

  • Noguchi Kohei, Mitsui Yoshifuru, Hiroi Masahiko, Umetsu Rie Y., Gouchi Jun, Uwatoko Yoshiya, Koyama Keiichi .  Effects of Substituted Elements on Spin Reorientation in Mn<sub>2−</sub><i><sub>x</sub></i>Fe<i><sub>x</sub></i>Sb<sub>1−</sub><i><sub>y</sub></i>Sn<i><sub>y</sub></i> .  MATERIALS TRANSACTIONS61 ( 8 ) 1492 - 1495   2020.8Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:The Japan Institute of Metals and Materials  

    <p>The spin reorientation and Curie temperature of Mn<sub>2−</sub><i><sub>x</sub></i>Fe<i><sub>x</sub></i>Sb<sub>1−</sub><i><sub>y</sub></i>Sn<i><sub>y</sub></i> (0 ≤ <i>x</i>, <i>y</i> ≤ 0.15) compound were investigated by magnetization measurements. Spin reorientation temperature increased from 255 K at <i>x</i> = 0 to 383 K at <i>x</i> = 0.15, whereas it almost unchanged by Sn substitution. Curie temperature decreased down to 518 K with both Fe and Sn substitution. Substitution of Fe stabilized the ferrimagnetic state with magnetic moment lying in <i>c</i>-plane. Substitution of Sn induced the antiferromagnetic phase at low temperature. It was found that the magnetic hysteresis derived from quasi first-order magnetic phase transition exhibited at <i>x</i> ≥ 0.10 or <i>T</i> ≥ 300 K.</p>

    DOI: 10.2320/matertrans.mt-mn2019016

    Scopus

  • Koyama Keiichi, Onoue Masahira, Kobayashi Ryota, Mitsui Yoshifuru, Umetsu Rie Y., Uwatoko Yoshiya .  Magnetic Field Effect on Nitrogenation of Sm<sub>2</sub>Fe<sub>17</sub> .  MATERIALS TRANSACTIONS61 ( 8 ) 1487 - 1491   2020.8Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:The Japan Institute of Metals and Materials  

    <p>Nitrogenation of Sm<sub>2</sub>Fe<sub>17</sub> powder was performed under a zero field and a magnetic field of 5 T at 623, 673 and 743 K to clarify the magnetic field effect on nitrogenation. Applying a magnetic field of 5 T induced nitrogenation compared with zero-field nitrogenation, and almost fully nitride Sm<sub>2</sub>Fe<sub>17</sub>N<sub>2.9</sub> was obtained at 743 K. Mössbauer spectroscopy results suggested that a 5-T magnetic field promoted the phase transformation to the fully-nitride Sm<sub>2</sub>Fe<sub>17</sub>N<sub>3</sub> phase. The magnetic field effect was discussed based on the magnetic energy gain and magnetic properties of host Sm<sub>2</sub>Fe<sub>17</sub> and fully nitride Sm<sub>2</sub>Fe<sub>17</sub>N<sub>3</sub>.</p>

    DOI: 10.2320/matertrans.mt-mn2019012

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  • 三井好古,尾上昌平,小山佳一 .  磁場中反応を利用した選択的磁性材料合成 .  まてりあ59 ( 8 ) 422 - 428   2020.8Reviewed

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:日本金属学会  

    DOI: https://doi.org/10.2320/materia.59.422

    Other Link: https://www.jstage.jst.go.jp/article/materia/59/8/59_422/_article/-char/ja/

  • K Nagano, Y Okubo, Y Mitsui, K Koyama, S Fujii .  Ab-Initio Study on Structural and Magnetic Properties of Fe-Doped MnCoGe .  Mater. Trans.61 ( 8 ) 1434 - 1437   2020.8Reviewed

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    DOI: https://doi:10.2320/matertrans.MT-MN2019013

    Other Link: https://www.jstage.jst.go.jp/article/matertrans/61/8/61_MT-MN2019013/_article

  • K Noguchi, Y Mitsui, M Hiroi, RY Umetsu, J Gouchi, Y Uwatoko, K Koyama .  Effects of Substituted Elements on Spin Reorientation in Mn2-xFexSb1-ySny .  Mater. Trans.61 ( 8 ) 1492 - 1495   2020.8Reviewed

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    DOI: https://doi.org/10.2320/matertrans.MT-MN2019016

    Other Link: https://www.jstage.jst.go.jp/article/matertrans/61/8/61_MT-MN2019016/_article

  • Deguchi Takuya, Matsubayashi Kazuyuki, Uwatoko Yoshiya, Koyama Takehide, Kohara Takao, Nakamura Hiroyuki, Mitsui Yoshifuru, Koyama Keiichi .  Magnetic Measurements of Narrow-Gap Semiconductor FeSb<sub>2</sub> under High Pressure .  MATERIALS TRANSACTIONS61 ( 8 ) 1476 - 1479   2020.7Invited Reviewed

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    <p>Pressure effects on magnetic susceptibility χ and energy gap <i>E</i><sub>g</sub><sup>0</sup> of narrow-gap semiconductor FeSb<sub>2</sub> were investigated for the temperature range of 50–300 K and pressures up to 13 kbar. The estimated <i>E</i><sub>g</sub><sup>0</sup> for ambient pressure, <i>E</i><sub>g0</sub>(0), was 29 meV. By application of pressure, χ was suppressed, and <i>E</i><sub>g0</sub>(<i>P</i>) was estimated to be 52 meV for 13 kbar. The fourth-order expansion coefficient γ of the free energy in magnetization was positive and enhanced by applying pressures.</p>

    DOI: 10.2320/matertrans.mt-mn2019015

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  • Tanaka Anna, Yoshinaga Soshi, Mitsui Yoshifuru, Sasaki Hiroe, Kanomata Takeshi, Koyama Keiichi .  Magnetic Properties of Weak Itinerant Electron Ferromagnet Au<sub>4</sub>V .  MATERIALS TRANSACTIONS61 ( 8 ) 1473 - 1475   2020.7Reviewed

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    <p>The magnetization measurements were carried out for polycrystalline Au<sub>4</sub>V in magnetic fields up to 130 kOe. The spontaneous magnetic moment <i>p</i><sub>s</sub> was determined to be 0.255 μ<sub>B</sub>/V at 4 K by high field magnetization. The magnetization process was analyzed on the basis of Takahashi’s spin fluctuation theory for weak itinerant electron ferromagnets. The characteristic parameters of the spin fluctuation were estimated to be <i>T</i><sub>A</sub> = 1.3 × 10<sup>3</sup> K and <i>T</i><sub>0</sub> = 2.3 × 10<sup>3</sup> K using the data for 110–130 kOe.</p>

    DOI: 10.2320/matertrans.mt-mn2019011

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  • Y. Mitsui, T. Hagio, K. Takahashi, K. Koyama, .  High magnetic field effects on the solid-liquid reaction of Fe-Ga system .  ISIJ International60 ( 4 ) 807 - 811   2020.4Reviewed

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  • Kohei Noguchi, Ryota Kobayashi, Yoshifuru Mitsui, Rie Y. Umetsu, Jun Gouchi, Yoshiya Uwatoko, Keiichi Koyama .  Heat treatment effect on the magnetic properties and martensitic transformations of MnCoGe .  Journal of Magnetism and Magnetic Materials499   2020.4Reviewed

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    © 2019 Elsevier B.V. X-ray powder diffraction, differential scanning calorimetry, and magnetization measurements were performed to investigate the effects of heat treatment on the magnetic and structural properties of as-cast and aging treated MnCoGe. The martensitic transformation temperature of the as-cast sample was 526 K for its first heating cycle, which decreased with repeating thermal cycles of 300–1273 K. MnCoGe prepared by aging treatment of 873 K for 7 days showed a first-order magnetic transition, which was accompanied by a martensitic transformation at 307 K. However, the transformation was not detected when the aging temperature was increased up to 973 K. The martensitic transformation temperature and volume of the parent phase was found to have a positive correlation.

    DOI: 10.1016/j.jmmm.2019.166199

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  • M. Hamasaki, M. Yamaguchi, L. Chen, M. Obara, Y. Mitsui, K. Koyama .  Development of an educational tool: experiments on light diffraction and interference for high school physics students .  Rep. Pac. Sci. Kagoshima Univ.52   7 - 14   2019.12

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    DOI: http://hdl.handle.net/10232/00030849

    Other Link: http://hdl.handle.net/10232/00030849

  • Watanabe Yumi, Hagio Toshiaki, Kobayashi Ryota, Mitsui Yoshifuru, Koyama Keiichi .  Phase Formation of a Solid-Liquid Mn–Ga Diffusion Couple under a Magnetic Field .  MATERIALS TRANSACTIONS60 ( 10 ) 2195 - 2198   2019.10Reviewed

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    <p>In-field heat treatments of an Mn–Ga diffusion couple were performed at 773 K for 12, 24 and 48 h to investigate the phase formation under magnetic fields. Formation of the MnGa<sub>3</sub>, Mn<sub>2</sub>Ga<sub>5</sub>, MnGa, Mn<sub>3</sub>Ga<sub>2</sub> and β-Mn phases was confirmed for magnetic fields of 0 T and 5 T. For a diffusion-controlled process, there is a parabolic relationship between the thickness of the phase layers and annealing time for the MnGa and Mn<sub>2</sub>Ga<sub>5</sub> phases. The parabolic coefficients of MnGa and Mn<sub>2</sub>Ga<sub>5</sub> for a zero magnetic field were determined as 8.7 × 10<sup>−3</sup> µm<sup>2</sup>s<sup>−1</sup> and 4.6 × 10<sup>−1</sup> µm<sup>2</sup>s<sup>−1</sup> respectively. For a magnetic field of 5 T, the parabolic coefficients were evaluated as 11 × 10<sup>−3</sup> µm<sup>2</sup>s<sup>−1</sup> for the MnGa phase and 4.5 × 10<sup>−1</sup> µm<sup>2</sup>s<sup>−1</sup> for the Mn<sub>2</sub>Ga<sub>5</sub> phase.</p>

    DOI: 10.2320/matertrans.mt-maw2019013

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  • Onoue Masahira, Kobayashi Ryota, Mitsui Yoshifuru, Umetsu Rie Y., Uwatoko Yoshiya, Koyama Keiichi .  In-Field Heat Treatment Effect on Nitridation of Sm<sub>2</sub>Fe<sub>17</sub> .  MATERIALS TRANSACTIONS60 ( 10 ) 2179 - 2182   2019.10Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:The Japan Institute of Metals and Materials  

    <p>An in-field heat treatment furnace utilized for a magnet with a 50 mm room-temperature bore was made to study magnetic field effect on gas-solid reaction. Using this furnace, nitridation of Sm<sub>2</sub>Fe<sub>17</sub> powder was performed under a 5-T magnetic field and a 0.1-MPa nitrogen gas pressure for the temperature range 623 to 743 K. Applying a magnetic field of 5 T promoted nitridation by approximately 0.6 nitrogen atoms per formula unit compared with zero-field nitridation, and almost fully nitride Sm<sub>2</sub>Fe<sub>17</sub>N<sub>2.9</sub> was obtained at 743 K.</p>

    DOI: 10.2320/matertrans.mt-maw2019009

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  • R. Kobayashi, Y. Mitsui, R.Y. Umetsu, K. Takahashi, M. Mizuguchi, K. Koyama, .  Magnetic-Field-Induced Enhancement of Phase Transformation in Ferromagnetic τ-Mn-Al .  J. Japan Inst. Met. Mater.83 ( 6 ) 181 - 185   2019Magnetic-Field-Induced Enhancement of Phase Transformation in Ferromagnetic τ-Mn-AlReviewed

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  • S. Eto, Y. Fukuda, Y. Mitsui, M. Ito, K. Koyama and S. Fujii .  Stable Structure, Magnetic and Electronic Properties of (Mn,Cr)AlGe .  J. Phys. Soc. Jpn.88   064709   2019Stable Structure, Magnetic and Electronic Properties of (Mn,Cr)AlGeReviewed

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  • Y. Watanabe, T. Hagio, R. Kobayashi, Y. Mitsui, K. Koyama .  Phase Formation of a Solid-Liquid Mn­Ga Diffusion Couple under a Magnetic Field .  Mater. Trans. 60   2195 - 2198   2019Phase Formation of a Solid-Liquid Mn­Ga Diffusion Couple under a Magnetic FieldReviewed

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  • M. Onoue, R. Kobayashi, Y. Mitsui, R. Y. Umetsu, Y. Uwatoko, K. Koyama .  In-Field Heat Treatment Effect on Nitridation of Sm2Fe17 .  Mater. Trans. 60   2179 - 2182   2019In-Field Heat Treatment Effect on Nitridation of Sm2Fe17Reviewed

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  • R. Kobayashi, Y. Mitsui, K. Takahashi, S. Uda, K. Koyama .  In-field annealing and quenching for ferromagnetic MnBi under 19 T .  IEEE Trans. on Magn.55   1000204   2019In-field annealing and quenching for ferromagnetic MnBi under 19 TReviewed

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  • Y. Mitsui, R. Kobayashi, Y. Takanaga, A. Takaki, R.Y Umetsu, K. Takahashi, M. Mizuguchi, K. Koyama .  Different Magnetic Field Effects on the ϵ-τ Phase Transformation Between (Mn, Zn)-Al and Mn-Al-C .  IEEE Trans. on Magn.55   2100704   2019Different Magnetic Field Effects on the ϵ-τ Phase Transformation Between (Mn, Zn)-Al and Mn-Al-CReviewed

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  • H. Masumitsu, S. Yoshinaga, Y. Mitsui, R.Y. Umetsu, M. Hiroi, Y. Uwatoko, K. Koyama .  Weak itinerant-electron ferromagnetism of CrAlGe modified by 3d transition metal .  J. Magn. Magn. Mater.492   165677   2019Weak itinerant-electron ferromagnetism of CrAlGe modified by 3d transition metalReviewed

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  • M. Hamasaki, M. Yamaguchi, L. Chen, M. Obara, Y. Mitsui, K. Koyama .  An educational tool for visualizing acoustic phenomena and measuring velocity, frequency and wavelength of sound waves .  Rep. Pac. Sci. Kagoshima Univ.51   1 - 8   2018.12An educational tool for visualizing acoustic phenomena and measuring velocity, frequency and wavelength of sound waves

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  • M. Hamasaki, M. Yamaguchi, L. Chen, M. Obara, Y. Mitsui, K. Koyama .  Development of a simple educational tool of calorimetry for high school students .  Rep. Pac. Sci. Kagoshima Univ.51   9 - 13   2018.12Development of a simple educational tool of calorimetry for high school students

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  • Kohei Noguchi, Hayato Masumitsu, Yoshifuru Mitsui, Rie Y. Umetsu, Masahiko Hiroi, Yoshiya Uwatoko, Keiichi Koyama .  Magnetic properties of Mn<inf>1-x</inf>TM<inf>x</inf>AlGe (TM = V, Fe, Cu) with Cu<inf>2</inf>Sb-type structure .  AIP Advances8 ( 10 )   2018.10Reviewed

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    © 2018 Author(s). The magnetic properties of Mn1-xTMxAlGe (TM = V, Fe and Cu) were investigated for x ≤ 0.2. The spontaneous magnetization decreased with increasing x. A remarkable decrease in the Curie temperature TC was observed for TM = Fe. For ferromagnetic MnAlGe (x = 0) and TM = nonmagnetic Cu (x = 0.2), Curie-Weiss law was confirmed. The compounds with TM = V and Fe (x = 0.2) did not show Curie-Weiss law, and the data of reciprocal susceptibility vs. temperature bent, indicating change of the magnetism from ferromagnetism. Obtained results suggested that the magnetic moments of V and Fe were aligned antiparallel to those of Mn, resulting in the ferrimagnetism-like behavior.

    DOI: 10.1063/1.5043069

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  • K. Noguchi, H. Masumitsu, Y. Mitsui, R.Y. Umetsu, M. Hiroi, Y. Uwatoko, K. Koyama, .  Magnetic properties of Mn1-xTMxAlGe (TM = V, Fe, Cu) with Cu2Sb-type structure .  AIP Advances 8   101433   2018.10Reviewed

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    DOI: https://doi.org/10.1063/1.5043069

    Other Link: https://aip.scitation.org/doi/full/10.1063/1.5043069

  • H. Masumitsu, S. Yoshinaga, Y. Mitsui, R.Y. Umetsu, M. Hiroi, Y. Uwatoko, K. Koyama .  Cu-substitution effects on the magnetic properties of weak itinerant electron ferromagnet CrAlGe .  AIP Advances 8   101426   2018.10Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: https://doi.org/10.1063/1.5043105

    Other Link: https://aip.scitation.org/doi/full/10.1063/1.5043105

  • Y. Okubo, S. Eto, Y. Mitsui, K. Koyama, S. Fujii .  Ab initio investigation of Fe substitution effect on magnetostructural transition of CoMnGe .  AIP Advances 8   101432   2018.8Reviewed

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    DOI: https://doi.org/10.1063/1.5042834

    Other Link: https://aip.scitation.org/doi/full/10.1063/1.5042834

  • Hayato Masumitsu, Soshi Yoshinaga, Yoshifuru Mitsui, Rie Y. Umetsu, Masahiko Hiroi, Yoshiya Uwatoko, Keiichi Koyama .  Magnetic and structural properties of Mn<inf>1−</inf><inf>x</inf>Cr<inf>x</inf>AlGe (0 ≤ x ≤ 1.0) .  Journal of Magnetism and Magnetic Materials456   104 - 107   2018.6Reviewed

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    © 2018 Elsevier B.V. The magnetic and structural properties of Mn1−xCrxAlGe (0 ≤ x ≤ 1.0) compounds were investigated. The spontaneous magnetization Ms and Curie temperature TC of Mn1−xCrxAlGe has a cusp at x = 0.2. The maximum values of Ms and TC are 1.74 μB/f.u. and 601 K, respectively. It was found that the tetragonal Cu2Sb-type structure was stable for 0 ≤ x ≤ 0.75, whereas orthorhombic TiSi2-type structure was observed for x ≥ 0.8. The reciprocal susceptibility as a function of temperature suggested that the magnetic moment of Cr is antiferromagnetically coupled with that of Mn in Cu2Sb-type structure.

    DOI: 10.1016/j.jmmm.2018.02.022

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  • Masahiko Hiroi, Syunya Ishikuma, Iduru Shigeta, Keiichi Koyama, Akihiro Kondo, Koichi Kindo, Hirotaka Manaka, Norio Terada .  Magnetization and magnetic phase diagram of Heusler compounds Fe3-y(Mn1-xV x ) y Si (y = 1 and 1.5) .  Journal of Physics: Conference Series969 ( 1 )   2018.4Reviewed

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:Institute of Physics Publishing  

    Fe2MnSi exhibits a ferromagnetic transition at TC and another transition to a phase with antiferromagnetic components at a low temperature of TA . By substituting V for Mn, so as to obtain Fe2Mn1-xV x Si, TA decreases with x and then vanishes around x ∼ 0.2. In this study, the magnetic transitions are investigated by magnetization measurements for Fe2Mn1-xV x Si (y = 1, 0 ≤ x ≤ 0.2) in high magnetic fields up to ∼70 T and for Fe1.5(Mn1-xV x )1.5Si (y = 1.5, 0 ≤ x ≤ 0.1) up to 5 T. For y = 1.5, with increasing x, TC increases and TA decreases as for y = 1, and the rate of the decrease in TA with x is slightly smaller than for y=1. In the low magnetic field region, TA for y = 1 does not significantly change due to the magnetic field but a distinct decrease is observed in high fields. The critical field at 0 K of this transition in Fe2MnSi is found to be larger than 70 T, and with increasing x, the critical field decreases corresponding to the decrease of TA at zero field.

    DOI: 10.1088/1742-6596/969/1/012099

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  • Soshi Yoshinaga, Yoshifuru Mitsui, Rie Y. Umetsu, Yoshiya Uwatoko, Keiichi Koyama .  Pressure Effect on Magnetic Properties of Weak Itinerant Electron Ferromagnet CrAlGe .  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN87 ( 1 )   2018.1Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:PHYSICAL SOC JAPAN  

    The Pressure effect on the magnetic properties of the weak itinerant electron ferromagnet CrAlGe was investigated at pressures up to 1.0 GPa. The spontaneous magnetic moment p(s) and Curie temperature T-C decreased with increasing applied pressure P. The pressure derivatives of p(s) and T-C were dp(s)/dP = -3.98 x 10(-5) mu(B)/MPa and dT(C)/dP = -6.58 x 10 K-3/MPa, respectively. These obtained results are discussed on the basis of Takahashi's spin fluctuation theory for weak itinerant electron ferromagnets. The characteristic parameters T-0 and T-A increased with pressure.

    DOI: 10.7566/JPSJ.87.014701

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  • Y. Mitsui, Y. Matsumoto, Y. Uwatoko, M. Hiroi, K. Koyama .  Magnetic relaxation dynamics in thermally arrested Cr-modified Mn2Sb .  J. Magn. Magn. Mater.461   62 - 68   2018Magnetic relaxation dynamics in thermally arrested Cr-modified Mn2SbReviewed

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  • Y. Mitsui, K. Koyama, M. Ohtsuka, R.Y. Umetsu, R. Kainuma, K. Watanabe .  High field X-ray diffraction study for Ni46.4Mn38.8In12.8Co2.0 metamagnetic shape memory film .  Metals7   364   2018High field X-ray diffraction study for Ni46.4Mn38.8In12.8Co2.0 metamagnetic shape memory filmReviewed

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  • S. Yoshinaga, Y. Mitsui, R. Y. Umetsu, Y. Uwatoko, K. Koyama .  Pressure effect on magnetic properties of weak itinerant electron ferromagnet GrAlGe .  J. Phys. Soc. Jpn87   014701   2018Pressure effect on magnetic properties of weak itinerant electron ferromagnet GrAlGeReviewed

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  • M. Onoue, R. Kobayashi, Y. Mitsui, M.Hiroi, K. Takahashi, A. Kondo, K. Kindo, Y. Uwatoko, K. Koyama .  Magnetic and Structural Properties of MnCoGe with Minimal Fe and Sn Substitution .  Mater. Trans. 59   1645 - 1650   2018Magnetic and Structural Properties of MnCoGe with Minimal Fe and Sn SubstitutionReviewed

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  • M. Hiroi, S. Ishikuma, I. Shigeta, K. Koyama, A. Kondo, K. K., H. Manaka, N. Terada .  Magnetization and magnetic phase diagram of Heusler compounds Fe3−y(Mn1−xVx)ySi (y= 1 and 1.5) .  J. Phys.: Conf. Ser.969   012099-1 - 012099-4   2018Magnetization and magnetic phase diagram of Heusler compounds Fe3−y(Mn1−xVx)ySi (y= 1 and 1.5)Reviewed

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  • H. Masumitsu, S. Yoshinaga, Y. Mitsui, R.Y. Umetsu, M. Hiroi, Y. Uwatoko, K. Koyama .  Magnetic and structural properties of Mn1-xCrxAlGe (0 ≤ x ≤ 1.0) .  J. Magn. Magn. Mater. 456   104 - 107   2018Magnetic and structural properties of Mn1-xCrxAlGe (0 ≤ x ≤ 1.0)Reviewed

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  • A.N. Nwodo, R. Kobayashi, T. Wakamori, Y. Matsumoto, Y. Mitsui, R.Y. Umetsu, M. Hiroi, K. Takahashi, Y. Uwatoko, K. Koyama .  Magnetic Phase Transition of Mn1.9Fe0.1Sb0.9Sn0.1 .  IEEE Magn. Lett.9   1400204-1 - 1400204-4   2018Magnetic Phase Transition of Mn1.9Fe0.1Sb0.9Sn0.1Reviewed

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  • R. Kobayashi, Y. Mitsui, K. Takahashi, S. Uda, K. Koyama .  In-field annealing and quenching for ferromagnetic MnBi under 19 T .  IEEE Trans. on Magn.55   1000204-1 - 1000204-4   2018In-field annealing and quenching for ferromagnetic MnBi under 19 TReviewed

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  • Y. Mitsui, R. Kobayashi, Y. Takanaga, A. Takaki, R.Y Umetsu, K. Takahashi, M. Mizuguchi, K. Koyama .  Different Magnetic Field Effects on the ϵ-τ Phase Transformation Between (Mn, Zn)-Al and Mn-Al-C .  IEEE Trans. on Magn.55   2100704-1 - 2100704-4   2018Different Magnetic Field Effects on the ϵ-τ Phase Transformation Between (Mn, Zn)-Al and Mn-Al-CReviewed

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  • Y. Mitsui, R.Y Umetsu, K. Takahashi, K. Koyama .  Reactive sintering process of ferromagnetic MnBi under high magnetic fields .  J. Magn. Magn. Mater.453   231 - 235   2018Reactive sintering process of ferromagnetic MnBi under high magnetic fieldsReviewed

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  • Nwodo Adline N., Kobayashi Ryota, Wakamori Taoto, Matsumoto Yoshihiro, Mitsui Yoshifuru, Hiroi Masahiko, Takahashi Kohki, Umetsu Rie Y., Uwatoko Yoshiya, Koyama Keiichi .  Quasi-First Order Magnetic Transition in Mn<sub>1.9</sub>Fe<sub>0.1</sub>Sb<sub>0.9</sub>Sn<sub>0.1</sub> .  MATERIALS TRANSACTIONS59 ( 3 ) 348 - 352   2018Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:The Japan Institute of Metals and Materials  

    <p>The magnetic and structural properties of ferrimagnetic (FRI) Mn<sub>1.9</sub>Fe<sub>0.1</sub>Sb<sub>0.9</sub>Sn<sub>0.1</sub> with a Cu<sub>2</sub>Sb-type tetragonal structure were studied by magnetization and high field X-ray diffraction (XRD) measurements in 10 ≤ <i>T</i> ≤ 773 K and in magnetic fields μ<sub>0</sub><i>H</i> up to 5 T. The lattice parameters <i>a</i> and <i>c</i> at 285 K were estimated to be 0.407 nm and 0.655 nm, respectively. The saturation magnetization at 10 K was determined to be 39.1 Am<sup>2</sup>/kg. It was observed that a first order magnetic transition (FOMT) with a thermal hysteresis occurred in the vicinity of 310 K under low magnetic fields. This FOMT disappeared easily by applying magnetic fields over 0.4 T.</p>

    DOI: 10.2320/matertrans.m2017291

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  • K. Koyama, M. Yamashita, R. Kobayashi, Y. Mitsui, K. Takahashi, S. Uda .  Development of a compact quenching furnace for use in high magnetic fields up to 15 T .  Rep. Pac. Sci. Kagoshima Univ.50   1 - 5   2017.12Development of a compact quenching furnace for use in high magnetic fields up to 15 T

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  • K. Koyama, D. Shimada, Y. Adachi, Y. Mitsui, M. Hiroi, Y. Uwatoko .  Magnetic properties of Mn2Sb1-xGex (x = 0.05, 0.08, 0.1) under high pressures .  Rep. Pac. Sci. Kagoshima Univ.50   12 - 18   2017.12Magnetic properties of Mn2Sb1-xGex (x = 0.05, 0.08, 0.1) under high pressures

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  • K. Koyama, A. Taira, Y. Mitsui, K. Takahashi, .  Characteristics of MnBi Synthesized by Solid-State Reaction Sintering Method in High Magnetic Field .  Rep. Pac. Sci. Kagoshima Univ.50   6 - 11   2017.12Characteristics of MnBi Synthesized by Solid-State Reaction Sintering Method in High Magnetic Field

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  • Mitsui Y. .  High field X-ray diffraction study for Ni<inf>46.4</inf>Mn<inf>38.8</inf>In<inf>12.8</inf>Co<inf>2.0</inf> metamagnetic shape memory film .  Metals7 ( 9 )   2017.9Reviewed

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    Publisher:Metals  

    DOI: 10.3390/met7090364

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  • D. Miyazaki, Y. Mitsui, R. Y. Umetsu, K. Takahashi, S. Uda, K. Koyama .  Enhancement of the Phase Formation Rate during In-Field Solid-Phase Reactive Sintering of Mn-Bi .  Mater. Trans.58   720 - 728   2017.4Enhancement of the Phase Formation Rate during In-Field Solid-Phase Reactive Sintering of Mn-BiReviewed

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  • S. Yoshinaga, Y. Mitsui, R.Y. Umetsu, Y. Uwatoko, K. Koyama .  Magnetic properties of weak itinerant electron ferromagnet CrAlGe .  J. Phys. Conf. Ser.868   012018   2017.1Magnetic properties of weak itinerant electron ferromagnet CrAlGeReviewed

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  • S. Yoshinaga, S. Miura, T. Kanomata, Y. Mitsui, K. Koyama .  Pressure Effect on Magnetism of Weak Itinerant Electron Ferromagnet Ni74.6Al25.4 .  IEEE Magn. Lett.8   140043   2017.1Pressure Effect on Magnetism of Weak Itinerant Electron Ferromagnet Ni74.6Al25.4Reviewed

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    DOI: 10.1109/LMAG.2016.2616843

  • T. Wakamori, Y. Mitsui, K. Takahashi, R.Y. Umetsu, Y. Uwatoko, M. Hiroi, K. Koyama .  Thermal Transformation Arrest Phenomena in Mn2Sb0.9Sn0.1 .  IEEE Magn. Lett.8   1402404   2017.1Thermal Transformation Arrest Phenomena in Mn2Sb0.9Sn0.1Reviewed

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  • M. Hiroi, T. Tazoko, H. Sano, I. Shigeta, K. Koyama, A. Kondo, K. Kindo, H. Manaka, N. Terada .  High-field magnetization of Heusler compound Fe2Mn1-xVxSi .  Phys. Rev. B95   014410   2017.1High-field magnetization of Heusler compound Fe2Mn1-xVxSiReviewed

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  • M. Hiroi, H. Sano, T. Tazoko, I. Shigeta, M. Ito, K. Koyama, H. Manaka, N, Terada, M. Fujii, A. Kondo, K. Kindo .  Magnetic and electrical properties of Heusler compounds Ru2Cr1-xXxSi (X = V, Ti) .  J. Alloys. Comp.694   1376 - 1382   2017.1Magnetic and electrical properties of Heusler compounds Ru2Cr1-xXxSi (X = V, Ti)Reviewed

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  • M. Yamashita, K. Abematsu, K. Takahashi, Y. Mitsui, K. Koyama .  Development of a compact quenching furnace used under high magnetic fields .  IEEE Magn. Lett.8   1400704   2017.1Development of a compact quenching furnace used under high magnetic fieldsReviewed

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  • R. Kobayashi, Y. Mitsui, R.Y. Umetsu, K. Takahashi, M. Mizuguchi, K. Koyama .  Annealing temperature and magnetic field effects for ε−τ transformation in Mn-Al alloys .  IEEE Magn. Lett.8   1400704   2017.1Annealing temperature and magnetic field effects for ε−τ transformation in Mn-Al alloysReviewed

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  • R. Kobayashi, Y. Mitsui, R.Y. Umetsu, K. Takahashi, M. Mizuguchi, K. Koyama .  Magnetic-Field-Induced Acceleration of Phase Formation in τ-Mn-Al .  Mater. Trans.58   1511 - 1518   2017Magnetic-Field-Induced Acceleration of Phase Formation in τ-Mn-AlReviewed

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  • Shigeta I. .  Fabrication and characterization of epitaxial films of superconductor NbN and highly spin-polarized heusler alloy Co<inf>2</inf>2Fe<inf>0.4</inf>Mn<inf>0.6</inf>Si .  IEEE Magnetics Letters8   1 - 5   2017Reviewed

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    DOI: 10.1109/LMAG.2017.2687878

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  • Kobayashi R. .  Effects of Annealing Temperature and Magnetic Field on the ϵ-τ Phase Transformation in Mn-Al Alloys .  IEEE Magnetics Letters8   2017Reviewed

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    DOI: 10.1109/LMAG.2016.2617859

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  • Misaki Yamashita, Ken-Ichi Abematu, Kohki Takahashi, Yoshifuru Mitsui, Keiichi Koyama .  Development of a Compact Quenching Furnace for Use in High Magnetic Fields .  IEEE MAGNETICS LETTERS8   2017Reviewed

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    DOI: 10.1109/LMAG.2016.2621733

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  • X. F. Miao, Y. Mitsui, A. Iulian Dugulan, L. Caron, N. V. Thang, P. Manuel, K. Koyama, K. Takahashi, N. H. van Dijk, and E. Brück .  Kinetic-arrest-induced phase coexistence and metastability in (Mn,Fe)2(P,Si) .  Phys. Rev. B94   094426   2016.12Kinetic-arrest-induced phase coexistence and metastability in (Mn,Fe)2(P,Si)Reviewed

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  • M. Onoue, K. Ozono, Y. Mitsui, M. Hiroi, R.Y. Umetsu, Y. Uwatoko, K. Koyama .  Magnetic properties of MnCo1-xFexGe (x = 0.08, 0.12) .  鹿児島大学理学部紀要49   11 - 15   2016.12Magnetic properties of MnCo1-xFexGe (x = 0.08, 0.12)

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  • A. Takaki, Y. Mitsui, D. Miyazaki, R.Y. Umetsu, K. Takahashi, K. Koyama .  Magnetic field effects on the morphology of Bi-Mn alloy prepared by solid-phase reactive sintering .  鹿児島大学理学部紀要49   17 - 21   2016.12Magnetic field effects on the morphology of Bi-Mn alloy prepared by solid-phase reactive sintering

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  • Magnetic Properties of Mn1.9Cu0.1Sb under High Pressure .  AIP Conf. Proc.1763   0020005   2016.8Magnetic Properties of Mn1.9Cu0.1Sb under High PressureReviewed

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    DOI: 10.1063/1.4961338

  • K. Abematsu, Y. Mitsui, A. Taira, D. Miyazaki, A. Takaki, R.Y. Umetsu, K. Takahashi, K. Koyama .  Magnetic Field Effects on Reactive Sintering of MnBi .  AIP Conf. Proc. 1763   0020010   2016.8Magnetic Field Effects on Reactive Sintering of MnBiReviewed

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  • T. Wakamori, Y. Mitsui, K. Takahashi, R.Y. Umetsu, M. Hiroi, K. Koyama .  High Field X-ray Diffraction Measurements of Mn2Sb0.95Ge0.05 .  AIP Conf. Proc. 1763   0020006   2016.8High Field X-ray Diffraction Measurements of Mn2Sb0.95Ge0.05Reviewed

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  • K. Ozono, Y. Mitsui, R. Y. Umetsu, M. Hiroi, K. Takahashi, K. Koyama .  Magnetic and Structural Properties of MnCo1-xFexGe (0 ≤ x ≤ 0.12) .  API Conf. Proc.1763   002003   2016.8Magnetic and Structural Properties of MnCo1-xFexGe (0 ≤ x ≤ 0.12)Reviewed

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  • K. Ozono, Y. Mitsui, M. Hiroi, R.Y. Umetsu, K. Takahashi, K. Matsubayashi, Y. Uwatoko, K. Koyama .  Magnetic and Structural Properties of Metamagnetic MnCo0.92Fe0.08Ge Compound .  Mater. Trans.57 ( 3 ) 316 - 320   2016.3Magnetic and Structural Properties of Metamagnetic MnCo0.92Fe0.08Ge CompoundReviewed

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    DOI: 10.2320/matertrans.M2015382

  • R. Onodera, K. Ohtake, K. Takahashi, S. Kimura, K. Watanabe, K. Koyama .  Observation of a Metamagnetic Transition of FeRh Alloy under High Magnetic Fields and High Temperatures .  J. Japan Inst. Met. Mater.80 ( 3 ) 186 - 191   2016.3Observation of a Metamagnetic Transition of FeRh Alloy under High Magnetic Fields and High TemperaturesReviewed

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    DOI: 10.2320/jinstmet.J2015055

  • Y. Mitsui, K. Abematsu, R.Y. Umetsu, K. Takahashi, K. Koyama .  Magnetic field effects on liquid-phase reactive sintering of MnBi .  J. Magn. Magn. Mater.400   304 - 306   2016.1Magnetic field effects on liquid-phase reactive sintering of MnBiReviewed

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    DOI: 10.1016/j.jmmm.2015.07.114

  • Kosuke Ozono, Yoshifuru Mitsui, Rie. Y. Umetsu, Masahiko Hiroi, Kohki Takahashi, Keiichi Koyama .  Magnetic and Structural Properties of MnCo1-xFexGe (0 &lt;= x &lt;= 0.12) .  FRONTIERS IN MATERIALS SCIENCE (FMS2015)1763   2016Reviewed

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    Structural, magnetic and thermal properties of ferromagnetic MnCo1-xFexGe (0 &lt;= x &lt;= 0.12) compounds were investigated. The Curie temperature T-C and the martensitic transformation temperature T-M of MnCoGe (x = 0) were determined to be 340 K and 510 K, respectively. With increasing x from 0 to 0.08, T-M decreased and reached room temperature (290 K) for x similar to 0.08. For x &gt; 0.09, MnCo1-xFexGe did not exhibit the martensitic transformation. The compound for x similar to 0.08 showed a first-order magnetic transition with a thermal hysteresis of 20 K and was accompanied by the martensitic transformation in the vicinity of room temperature. The phase diagram of MnCo1-xFex Ge (0 &lt;= x &lt;= 0.12) is presented.

    DOI: 10.1063/1.4961336

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  • S. Yoshinaga, Y. Mitsui, R.Y. Umetsu, K. Koyama .  Magnetic properties of Cr-based ternary compound CrAlGe .  Physics Procedia75   918 - 925   2015.12Magnetic properties of Cr-based ternary compound CrAlGeReviewed

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    DOI: 10.1016/j.phpro.2015.12.126

  • Y. Mitsui, Y. Yoshimine, R.Y. Umetsu, K. Matsubayashi, Y. Uwatoko, M. Hiroi, K. Koyama .  Pressure Effect on the Martensitic Transformation and Magnetic Properties of Mn2−xNi1+xGa .  鹿児島大学理学部紀要48   35 - 39   2015.12Pressure Effect on the Martensitic Transformation and Magnetic Properties of Mn2−xNi1+xGa

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    Other Link: http://hdl.handle.net/10232/26366

  • K. Koyama, D. Shimada, Y. Adachi, H. Orihashi, D. Mitsunaga, M. Hiroi, Y. Mitsui, S. Kimura, K. Matsubayashi, Y. Uwatoko .  Magnetic and electrical properties of Mn2Sb1−xZx (Z = Ge, Sn) under high pressures and high magnetic fields .  Rep. Fac. Sri., Kagoshima Univ.48   15 - 21   2015.12Magnetic and electrical properties of Mn2Sb1−xZx (Z = Ge, Sn) under high pressures and high magnetic fields

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    Authorship:Lead author   Language:English   Publishing type:Research paper (bulletin of university, research institution)  

    Other Link: http://hdl.handle.net/10232/26364

  • D. Miyazaki, Y. Mitsui, K. Abematsu, K. Takahashi, K. Watanabe, S. Uda, K. Koyama .  In-situ observation and differential thermal analysis of MnBi in high magnetic fields .  Physics Procedia75   1324 - 1331   2015.12In-situ observation and differential thermal analysis of MnBi in high magnetic fieldsReviewed

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    DOI: 10.1016/j.phpro.2015.12.148

  • R. Onodera, S. Kimura, K. Watanabe, Y. Yokoyama, A. Makino, K. Koyama .  Nucleation control for fine nano crystallization of Fe-based amorphous alloy by high-magnetic-field annealing .  J. Alloys Comp.637   213 - 218   2015.7Nucleation control for fine nano crystallization of Fe-based amorphous alloy by high-magnetic-field annealingReviewed

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  • Y. Mitsui, Y. Ikehara, K. Takahashi, S. Kimura, G. Miyamato, F. Furuhara, K. Watanabe, K. Koyama .  Fe-Fe3C binary phase diagram in high magnetic fields .  J. Alloys Comp.632   251 - 255   2015.3Fe-Fe3C binary phase diagram in high magnetic fieldsReviewed

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  • Yoshifuru Mitsui, Yuki Yoshimine, Rie Y. Umetsu, Kazuyuki Matsubayashi, Yoshiya Uwatoko, Masahiko Hiroi, Keiichi Koyama .  Pressure Effect on the Martensitic Transformation and Magnetic Properties of Mn2-xNi1+xGa .  鹿児島大学理学部紀要48   35 - 39   2015Pressure Effect on the Martensitic Transformation and Magnetic Properties of Mn2-xNi1+xGa

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  • Goto Junya, Kakimoto Takatoshi, Fujii Shinpei, Koyama Keiichi .  Site Preference and Stabilization of Antiferromagnetism in M-Substituted Mn<sub>2−</sub><i><sub>x</sub></i>M<i><sub>x</sub></i>Sb (M = Ti, Cr, Co, or Cu) .  MATERIALS TRANSACTIONS56 ( 3 ) 415 - 423   2015Reviewed

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    We applied first-principles total-energy calculations to several compounds Mn<sub>2−</sub><i><sub>x</sub></i>M<i><sub>x</sub></i>Sb (M = Ti, Cr, Co, or Cu) to calculate the total energy. The results indicate that the Ti and Cu (Cr and Co) atoms prefer the Mn(II) site to the Mn(I) site [Mn(I) to Mn(II)]. These results are consistent with experimental observations. The antiferromagnetism (AF) [ferrimagnetism (FR)] is more stable than FR (AF) upon decreasing (increasing) the distance between the Mn(II) and Sb atoms in the <i>z</i> direction in all Mn<sub>2−</sub><i><sub>x</sub></i>M<i><sub>x</sub></i>Sb systems. This result indicates that the environment around the Mn atom plays a very important role in the stabilization of the AF state, as is the case with Mn<sub>2</sub>Sb<sub>1−</sub><i><sub>x</sub></i>As<i><sub>x</sub></i> systems. For Mn<sub>2−</sub><i><sub>x</sub></i>Co<i><sub>x</sub></i>Sb systems, the atomic disorder between the Mn and Co atoms is insensitive to the relative stability of two magnetic phases AF and FR.

    DOI: 10.2320/matertrans.m2014417

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  • Y. Mitsui, R.Y. Umetsu, K. Koyama and K. Watanabe .  Magnetic-field-induced enhancement for synthesizing ferromagnetic MnBi phase by solid-state reaction sintering .  J. Alloys Comp.615   131 - 134   2014.12Magnetic-field-induced enhancement for synthesizing ferromagnetic MnBi phase by solid-state reaction sinteringReviewed

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  • 小山佳一, 五十嵐利行, 渡辺和雄 .  HfV2の強磁場と高圧下における磁気的,熱伝的及び構造的特性 .  鹿児島大学理学部紀要47   13 - 19   2014.12HfV2の強磁場と高圧下における磁気的,熱伝的及び構造的特性

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  • T. Kakimoto, J. Goto, S. Fujii, K. Koyama and S. Ishida .  Electronic and magnetic properties of Mn2Sb1-xAsx (x = 0, 0.5, 1) .  Mater. Trans. 55 ( 12 ) 1878 - 1884   2014.12Electronic and magnetic properties of Mn2Sb1-xAsx (x = 0, 0.5, 1)Reviewed

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  • T.M. Pan,C.H. Chen, J.L. Her, K. Koyama .  Comparison of structural and electrical properties of Lu2O3 and Lu2TiO5 gate dielectrics for alpha-InGaZnO thin-film transistors .  J. Appl. Phys.116 ( 19 ) 194510 - -4   2014.11Comparison of structural and electrical properties of Lu2O3 and Lu2TiO5 gate dielectrics for alpha-InGaZnO thin-film transistorsReviewed

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  • J.L. Her, T.M. Pan, J.H. Liu, H.J. Wang, C.H. Chen, K. Koyama .  Electrical characteristics of GdTiO3 gate dielectric for amorphous InGaZnO thin-film transistors .  Thin Solid Films569   6 - 9   2014.10Electrical characteristics of GdTiO3 gate dielectric for amorphous InGaZnO thin-film transistorsReviewed

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  • Y. Mitsui, K. Koyama, K. Oikawa, K. Watanabe .  Magnetic field effect on the liquid boundary of Bi-Mn binary system .  AIP Conference Proceedings1618   269 - 272   2014.10Magnetic field effect on the liquid boundary of Bi-Mn binary system

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  • T.M. Pan, F.H. Chen, M.N. Hung, J.L. Her, K. Koyama .  Structural Properties and Electrical Characteristics of High-kappa Tm2O3 Gate Dielectrics for InGaZnO Thin Film Transistors .  Sci. Adv. Mater. 6 ( 9 ) 1973 - 1978   2014.9Structural Properties and Electrical Characteristics of High-kappa Tm2O3 Gate Dielectrics for InGaZnO Thin Film TransistorsReviewed

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  • Y. Mitsui, R.Y.Umetsu, K. Koyama, K. Watanabe .  Magnetic-field-induced enhancement for synthesizing ferromagnetic MnBi phase by solid-state reaction sintering .  J. Alloys. Comp.615   131 - 134   2014.6Magnetic-field-induced enhancement for synthesizing ferromagnetic MnBi phase by solid-state reaction sinteringReviewed

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  • M. Yamamoto, K. Magishi, A. Hisada, T. Saito, K. Koyama, M. Takusari, H. Kato, C. Sekine .  NMR Study of Filled Skutterudite Pr0.9Ce0.1Ru4P12 .  JPS Conf. Proc.3   011003 (6 pages )   2014.6NMR Study of Filled Skutterudite Pr0.9Ce0.1Ru4P12Reviewed

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    DOI: 10.7566/JPSCP.3.011003

  • Mitsui Yoshifuru, Ikehara Yuki, Takahashi Kohki, Watanabe Kazuo, Koyama Keiichi .  Magnetic Field Effect on α→γ Transformation of Fe-C Alloys by Differential Thermal Analysis under High Magnetic Fields .  Netsu Sokutei41 ( 2 ) 43 - 48   2014.4Magnetic Field Effect on α→γ Transformation of Fe-C Alloys by Differential Thermal Analysis under High Magnetic FieldsReviewed

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    The magnetic field effect on the α–γ transformation of hypoeutectoid steels (Fe-0.1wt.%C, Fe-0.23wt.%C, and Fe-0.47wt.%C) were investigated by differential thermal analysis under high magnetic fields <i>B</i> up to 26 T. The magnetic field effects for the transformation temperatures A<sub>1</sub> (αFe + Fe<sub>3</sub>C → α-Fe + γ-Fe) and A<sub>3</sub> (α-Fe + γ-Fe → γ-Fe) were different from each other. The increment of A<sub>1</sub> induced by the magnetic field was independent from the carbon concentration. A<sub>1</sub> increased linearly for the magnetic field for <i>B</i> < 10 T, whereas A<sub>1</sub> increased quadratically for <i>B</i> > 20 T. A<sub>3</sub> for Fe-0.23 wt.%C increased quadratically against <i>B</i>. When the magnetic field of 26 T was applied, A<sub>1</sub> and A<sub>3</sub> for Fe-0.47wt.%C increased 35 K and 53 K, respectively. The magnetic field effects for the A<sub>1</sub> and A<sub>3</sub> are discussed on the basis of the gain of Zeeman energy for α-Fe.

    DOI: 10.11311/jscta.41.2_43

  • R. Onodera, S. Kimura, K. Watanabe, Y. Yokoyama, A. Makino and K. Koyama .  Crystallization kinetics of high iron concentration amorphous alloys under high magnetic fields .  J. Alloys Comp.604   8 - 11   2014.4Crystallization kinetics of high iron concentration amorphous alloys under high magnetic fieldsReviewed

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  • K. Abematsu, R.Y. Umetsu, R. Kainuma, T. Kanomata, K. Watanabe and K. Koyama .  Structural and magnetic properties of magnetic shape memory alloy Ni46Mn41In13 under magnetic fields .  Mater. Trans. 55   477 - 481   2014.4Structural and magnetic properties of magnetic shape memory alloy Ni46Mn41In13 under magnetic fieldsReviewed

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  • 三井好古、小山佳一、淡路智、渡辺和雄 .  強磁場中熱分析 -相平衡への強磁場効果 .  低温工学49 ( 1 ) 11 - 18   2014.1強磁場中熱分析 -相平衡への強磁場効果Reviewed

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  • T.M. Pan, H.C. Chen, J.H. Liu, F.H. Chen, J.L. Her, K. Koyama .  Comparison of High-kappa Gd2O3 and GdTiO3 alpha-InGaZnO Thin-Film Transistors .  IEEE TRANSACTIONS ON ELECTRON DEVICES61 ( 1 ) 87 - 91   2014.1Comparison of High-kappa Gd2O3 and GdTiO3 alpha-InGaZnO Thin-Film TransistorsReviewed

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  • S. Mondal, J.L Her,K. Koyama, T.M. Pan .  Resistive switching behavior in Lu2O3 thin film for advanced flexible memory applications .  NANOSCALE RESEARCH LETTERS9   3(8)   2014.1Resistive switching behavior in Lu2O3 thin film for advanced flexible memory applicationsReviewed

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  • Y. Matsumoto, H. Orihashi, K. Matsubayashi, Y. Uwatoko, M. Hiroi, K. Koyama .  Magnetic field effect on magnetic and electrical properties of Mn2-xCuxSb .  IEEE Trans. Magn.50   1000704 - -4   2014.1Magnetic field effect on magnetic and electrical properties of Mn2-xCuxSbReviewed

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  • K. Ohtake, Y. Mitsui, K. Takahashi, R. Onodera,S. Kimura, K. Watanabe and K. Koyama .  X-ray diffraction measurements of the Fe-Rh alloy under high magnetic fields and at high temperatures .  IEEE Trans. Magn.50   1001404 - -4   2014.1X-ray diffraction measurements of the Fe-Rh alloy under high magnetic fields and at high temperaturesReviewed

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  • T.M. Pan, C.H. Chen, J.H. Liu, J.L. Her and. K. Koyama .  Electrical and reliability characteristics of high-kappa HoTiO3 alpha-InGaZnO thin-film transistors .  IEEE Trans. Device Lett35   66 - 68   2014.1Electrical and reliability characteristics of high-kappa HoTiO3 alpha-InGaZnO thin-film transistorsReviewed

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  • Y. Yoshimine, D. Mitsunaga, H. Orihashi, D. Shimada, M. Hiroi, R. Onodera, S. Kimura, K. Takahashi and K. Koyama .  Magnetic and electrical properties of Mn2-xNi1+xSb .  IEEE Trans. Magn50   1001204 - -4   2014.1Magnetic and electrical properties of Mn2-xNi1+xSbReviewed

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  • T. Tsutaoka, K. Obata, S. Cheyvuth and K. Koyama .  Magnetic phase transitions in Er7Rh3 studied on single crystals .  J. Alloy Comp.606   214 - 218   2014Magnetic phase transitions in Er7Rh3 studied on single crystalsReviewed

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  • S. Mondal, J.L.Her, K. Koyama, and T.M Pan .  Resistive switching behavior in Lu2O3 thin film for advanced flexible memory applications .  Nanoscale Research Lett.9   3   2014Resistive switching behavior in Lu2O3 thin film for advanced flexible memory applicationsReviewed

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  • Kakimoto Takatoshi, Goto Junya, Fujii Shinpei, Koyama Keiichi, Ishida Shoji .  Electronic and Magnetic Properties of Mn<sub>2</sub>Sb<sub>1−</sub><i><sub>x</sub></i>As<i><sub>x</sub></i> (<I>x</I> = 0,0.5,1) .  MATERIALS TRANSACTIONS55 ( 12 ) 1878 - 1884   2014

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    The electronic and magnetic properties of Mn<sub>2</sub>Sb<sub>1−</sub><i><sub>x</sub></i>As<i><sub>x</sub></i> (where <I>x</I> = 0,0.5,1) are investigated from first-principles total-energy calculations. The predicted magnetic ground states (ferrimagnetism for <i>x</i> = 0 and antiferromagnetism for <i>x</i> = 1) are in agreement with experimental observations; however, this is not the case for <i>x</i> = 0.5. Here, it is found that the artificial change of the surrounding atoms of Mn stabilizes the antiferromagnetism. A similar change stabilizes ferrimagnetism (antiferromagnetism) for <i>x</i> = 1 (<i>x</i> = 0). These results indicate that the environment around the Mn atoms plays a very important role in the stabilization of antiferromagnetism in the Mn<sub>2</sub>Sb<sub>1−</sub><i><sub>x</sub></i>As<i><sub>x</sub></i> system. In addition, an analysis of the sign of an effective exchange interaction as a function of the distance between the Mn atoms is performed.

    DOI: 10.2320/matertrans.m2014251

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  • Yoshifuru Mitsui, Keiichi Koyama, Katsunari Oikawa, Kazuo Watanabe .  Magnetic Field Effect on the Liquidus Boundary of Bi-Mn Binary System .  INTERNATIONAL CONFERENCE OF COMPUTATIONAL METHODS IN SCIENCES AND ENGINEERING 2014 (ICCMSE 2014)1618   269 - 272   2014Reviewed

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    The magnetic field effect (MFE) on liquidus boundary of Bi-Mn binary system was investigated by differential thermal analysis (DTA) and the computer coupling of phase diagram method (CALPHAD). The liquidus boundary for Bi-18at.% Mn and Bi-24at.%Mn rose clearly by the application of the magnetic fields. The MFE for liquidus boundary temperature T-liq changed from Delta T-liq proportional to B-2 to Delta T-liq proportional to B because of the large increase of the peritectic temperature from BiMn and BiMn1.08 by the application of magnetic field.

    DOI: 10.1063/1.4897725

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  • Abematsu Kenichi, Umetsu Rie Y., Kainuma Ryosuke, Kanomata Takeshi, Watanabe Kazuo, Koyama Keiichi .  Structural and Magnetic Properties of Magnetic Shape Memory Alloy Ni<sub>46</sub>Mn<sub>41</sub>In<sub>13</sub> under Magnetic Fields .  MATERIALS TRANSACTIONS55 ( 3 ) 477 - 481   2014

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    The structural and magnetic properties of Heusler alloy Ni<sub>46</sub>Mn<sub>41</sub>In<sub>13</sub> were studied by magnetization and X-ray powder diffraction measurements in the 4.5–350 K temperature range and in magnetic fields up to 5 T. The alloy undergoes martensitic transformation from a <i>L</i>2<sub>1</sub>-type cubic structure with <i>a</i><sub>c</sub> = 0.600 nm at 293 K to a six-layered monoclinic (6<i>M</i>) structure in the transition temperature of 160–230 K. The lattice parameters for the 6<i>M</i> structure were estimated to be <i>a</i><sub>m</sub> = 0.441 nm, <i>b</i><sub>m</sub> = 0.557 nm, <i>c</i><sub>m</sub> = 1.30 nm, α<sub>m</sub> = 90.0°, β<sub>m</sub> = 94.0°, and γ<sub>m</sub> = 90.0° at 75 K. In this transformation from the <i>L</i>2<sub>1</sub> to 6<i>M</i> structures, the cell volume contracts by 0.34% at 8 K. In addition, we observed the magnetic field-induced reverse transformation of this alloy.

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  • Ching-Hung Chen, Jim-Long Her, Tung-Ming Pan, Fu-Chien Chiu, Keiichi Koyama .  Structural Properties and Electrical Characteristics of high-kappa GdTiO3 Gate Dielectrics for InGaZnO Thin-Film Transistors .  2014 TENTH INTERNATIONAL VACUUM ELECTRON SOURCES CONFERENCE (IVESC)   2014Reviewed

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    We investigated the structural properties and electrical characteristics of GdTiO3 dielectrics for IGZO TFT devices. We used XRD, XPS, and AFM to examine the structural, compositional, and morphological features of the GdTiO3 film, respectively. The IGZO TFT featuring a GdTiO3 gate dielectric exhibited a large field-effect mobility of 32.3 cm(2) V-s, a small threshold voltage of 0.14 V, a high Ion/Ioff current ratio of 4.2 x 10(8), and a low subthreshold swing of 213 mV/decade.

    DOI: 10.1109/IVESC.2014.6891962

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  • M. Mitsui, R.Y. Umetsu, M. Saito, K. Koyama, H. Kawarada .  Synthesis and diffusion of MnBi in high magnetic fields .  The International Symposium on Ecotopia Science 2013 and The 5th International Symposium on Advanced Materials Development and Integration of Novel Structural Metallic and Inorganic Materials (ISETS’13 and AMDI-4)   1317   2013.12Synthesis and diffusion of MnBi in high magnetic fields

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  • J. Goto, T. Kakimoto, S. Fujii and K. Koyama .  Magnetic and electronic structures and Cobalt or Copper substituted Mn2Sb .  Mater. Trans.54 ( 12 ) 2309 - 2312   2013.12Magnetic and electronic structures and Cobalt or Copper substituted Mn2SbReviewed

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  • 後藤純哉、柿本貴俊、藤井伸平、小山佳一 .  Electronic and magnetic structures of Cobalt substituted Mn2Sb .  日本金属学会誌77 ( 10 ) 461 - 465   2013.10Electronic and magnetic structures of Cobalt substituted Mn2SbReviewed

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  • Y. Mitsui, K. Oikawa, K. Koyama and K. Watanabe .  Thermodynamic assessment for the Bi-Mn binary phase diagram in high magnetic fields .  J. Alloys Comp.577   315 - 319   2013.8Thermodynamic assessment for the Bi-Mn binary phase diagram in high magnetic fieldsReviewed

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  • Y. Mitsui, Y. Ikehara, K. Watanabe, E.S. Choi, E.C. Palm and K. Koyama .  Thermal analysis on MnBi in high magnetic fields up to 45 T .  J. Korean Phys. Soc.62   1769 - 1772   2013.8Thermal analysis on MnBi in high magnetic fields up to 45 TReviewed

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  • Daisuke Shimada, Hiroki Orihashi, Daisuke Mitsunaga, Masakazu Ito, Masahiko Hiroi, Keiichi Koyama, Reisho Onodera, Kohki Takahashi, Kazuyuki Matsubayashi, Yoshiya Uwatoko .  Magnetic properties of Mn2Sb1-x Ge (x) (0.05 a parts per thousand currency sign x a parts per thousand currency sign 0.2) in high magnetic fields .  JOURNAL OF THE KOREAN PHYSICAL SOCIETY63 ( 3 ) 747 - 750   2013.8Reviewed

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    Magnetization and electrical resistivity measurements were carried out for polycrystalline Mn2Sb1-x Ge (x) (0.05 a parts per thousand currency sign x a parts per thousand currency sign 0.2) in magnetic fields up to 16 T in the 4.2 - 600 K temperature range in order to investigate the magnetic and the electrical properties under high magnetic fields. Mn2Sb0.92Ge0.08 showed a Curie temperature, T (C) , of 532 K and a first order magnetic transition from a ferrimagnetic (FRI) to an antiferromagnetic (AFM) phase at T (t) = 230 K with decreasing temperature in a zero magnetic field. With increasing x, T (C) decreased and T (t) increased. For Mn2Sb0.92Ge0.08, a matamagnetic transition from an AFM to a FRI phase was observed at 215 K. The magnetic phase diagram of Mn2Sb1-x Ge (x) is presented.

    DOI: 10.3938/jkps.63.747

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  • R. Onodera, S. Kimura, K. Watanabe, Y. Yokoyama, A. Makino and K. Koyama .  Isothermal Crystallization of Iron-Based Amorphous Alloys in a High Magnetic Field .  Mater. Trans54 ( 7 ) 1232 - 1235   2013.7Isothermal Crystallization of Iron-Based Amorphous Alloys in a High Magnetic FieldReviewed

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  • D. Shimada, H. Orihashi, D. Mitsunaga, M. Ito, M. Hiroi, K. Koyama, R. Onodera, K. Takahashi, K. Matsubayashi, Y. Uwatoko .  Magnetic properties of Mn2Sb1-xGex (0.05 ? x ? 0.2) in high magnetic fields .  J. Korean Phys. Soc.62   747 - 750   2013.7Magnetic properties of Mn2Sb1-xGex (0.05 ? x ? 0.2) in high magnetic fieldsReviewed

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  • A.V. Andreev, E.A. Tereshina, D.I. Gorbunov, E. Santava, J. Sebek, M. Zacek, Y. Homma, Y. Shiokawa, I. Satoh, t. Yamamura, T. Komatsubara, K. Watanabe and K. Koyama .  Magnetic anisotropy in intermetallic compounds containing both Uranium and 3d-metal .  Phys. Metals and Metallography114   727 - 733   2013.7Magnetic anisotropy in intermetallic compounds containing both Uranium and 3d-metalReviewed

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  • T. Shigeoka, T. Fujiwara, K. Koyama, S. Kimura and K. Watanabe .  Multi-step metamagnetic processes of PrPd2Si2 single crystal .  J. Korean Phys. Soc.63   567 - 570   2013.7Multi-step metamagnetic processes of PrPd2Si2 single crystalReviewed

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  • Y. Adachi, T. Kitai, K. Koyama, H. Yoshika, and T. Kaneko .  Magnetization curves of TbZn2 in high magnetic fields .  J. Korean Phys. Soc.62   2077 - 2079   2013.7Magnetization curves of TbZn2 in high magnetic fieldsReviewed

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  • M. Hiroi, K. Uchida, I. Shigeta, M. Ito and K. Koyama .  Antiferromagnetic transition in Ru2CrSi in magnetic fields .  J. Korean Phys. Soc.62   2068 - 2072   2013.7Antiferromagnetic transition in Ru2CrSi in magnetic fieldsReviewed

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  • X. Xu, T. Kihara, M. Tokunagam, A. Matsuo, W. Ito, R.Y. Umetsu, K. Koyama, R. Kainuma .  Thermal transformation arrest phenomenon in the metamagnetic shape memory alloys .  ICFSMA’13 The Fourth International Conference on Ferromagnetic Shape Memory Alloys, Conference Proceedings   26 - 27   2013.6Thermal transformation arrest phenomenon in the metamagnetic shape memory alloys

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  • H. Orihashi, M. Hiroi, Y. Mitsui, K. Takahashi, K. Watanabe, K. Matsubayashi, Y. Uwatoko and K. Koyama, .  Magnetic and Structural Properties of Mn1.8Co0.2Sb under High Magnetic Fields .  Mater. Trans.54 ( 6 ) 969 - 973   2013.6Magnetic and Structural Properties of Mn1.8Co0.2Sb under High Magnetic FieldsReviewed

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  • T. Sakon, K. Koyama, O. Kamiya, S. Awaji, S. Nakamura, T. Nojima, H. Nojiri, K. Watanabe, and M. Hiroi .  High-field magnetization measurements of Fe2MnSi .  J. Phys. Soc. Jpn.82 ( 4 ) 44802 - -4   2013.4High-field magnetization measurements of Fe2MnSiReviewed

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  • S. Kimura, K. Okunishi, M. Hagiwara, K. Kindo, Z. He, T. Taniyama, M. Itoh, K. Koyama, and K. Watanabe .  Collapse of Magnetic Order of the Quasi One-Dimensional Ising-Like Antiferromagnet BaCo2V2O8 in Transverse Fields .  J. Phys. Soc. Jpn82 ( 3 ) 33706 - -4   2013.3Collapse of Magnetic Order of the Quasi One-Dimensional Ising-Like Antiferromagnet BaCo2V2O8 in Transverse FieldsReviewed

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  • K. Koyama, K. Watanabe, O. Tegus, E. Bruck, K.H.J. Buschow, F.R. de Boer .  X-Ray Powder Diffraction Studies on MnFeP0.78Ge0.22 in High Magnetic Fields .  J. Low Temp. Phys.170 ( 42130 ) 279 - 284   2013.3X-Ray Powder Diffraction Studies on MnFeP0.78Ge0.22 in High Magnetic FieldsReviewed

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  • Y. Mitsui, K. Koyama and K. Watanabe .  Bi-Mn Binary Phase Diagram in High Magnetic Fields .  Mater. Trans.54 ( 2 ) 242 - 245   2013.2Bi-Mn Binary Phase Diagram in High Magnetic FieldsReviewed

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  • R. Onodera, S. Kimura, K. Watanabe, S. Lee, Y. Yokoyama, A. Makino and K. Koyama .  Magnetic Field Effects on Crystallization of Iron-Based Amorphous Alloys .  Mater. Trans.54 ( 2 ) 188 - 191   2013.2Magnetic Field Effects on Crystallization of Iron-Based Amorphous AlloysReviewed

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  • I. Shigeta, Y. Sakuraba, S. Kimura, K. Koyama, K. Watanabe, K. Takanashi, and M. Hiroi, .  Transport and magnetic properties of fully-epitaxial superconducting NbN/half-metallic Heulser alloys Co2MnSi bilayer films .  J. Magn. Soc. Jpn37   222 - 226   2013.1Transport and magnetic properties of fully-epitaxial superconducting NbN/half-metallic Heulser alloys Co2MnSi bilayer filmsReviewed

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  • R.Y. Umetsu, D. Kikuchi, K. Koyama, K. Watanabe, Y. Yamaguchi, R. Kainuma, T. Kanomata .  Site occupancy and magnetic moment of Fe in Ni2Mn0.3Fe0.7Ga alloy by neutron powder diffraction study .  J. Alloy. Comp.580 ( 7 ) 506 - 511   2013.1Site occupancy and magnetic moment of Fe in Ni2Mn0.3Fe0.7Ga alloy by neutron powder diffraction studyReviewed

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  • Amitani H., Asakawa A., Ogiso K., Nakahara T., Ushikai M., Haruta I., Koyama K.I., Amitani M., Cheng K.c., Inui A. .  The role of adiponectin multimers in anorexia nervosa .  Nutrition29 ( 1 ) 203 - 206   2013.1

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    Objective: Anorexia nervosa (AN) continues to be a refractory disease because of its unknown pathogenesis. The role of adiponectin in AN has not been clarified. Moreover, few reports have described the relations between adiponectin isoforms and AN in the physical and psychological states. Therefore, we measured plasma adiponectin and its isoforms levels in patients with AN to examine their roles in AN. Methods: Eighteen women participated in this study: nine patients with AN and nine age-matched healthy controls. We examined plasma adiponectin and its isoforms levels in all subjects and administered three types of psychological test to patients with AN: the Eating Disorders Inventory-2, the Maudsley Obsessional-Compulsive Inventory, and the Beck Depression Inventory-2. Results: We found that the percentage of high-molecular-weight (HMW) to total adiponectin (%HMW) was significantly low and the percentage of low-molecular-weight (LMW) to total adiponectin (%LMW) was significantly high in the AN group compared with the control group. The %HMW positively and the %LMW negatively correlated with body mass index in the entire study population. The %HMW was also positively correlated with psychological symptoms such as social insecurity or cleaning evaluated with the Eating Disorders Inventory-2 or the Maudsley Obsessional-Compulsive Inventory. Conclusions: Our study indicates that all adiponectin isoforms should be evaluated in patients with AN in addition to total adiponectin. The decreased %HMW and the increased %LMW that were correlated with the body mass index and some components of psychopathology in our patients may indicate a complex role of adiponectin isoforms in maintaining energy homeostasis and emotion during extreme malnourishment. © 2013 Elsevier Inc.

    DOI: 10.1016/j.nut.2012.07.011

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  • K. Watanabe, Y. Mitsui, K. Koyama .  Heat-treatment processing for MnBi in high magnetic fields .  Advances in Science and Technology78   19 - 24   2013Heat-treatment processing for MnBi in high magnetic fieldsReviewed

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  • Shigeta I., Sakuraba Y., Molenaar C. G., Beukers J. N., Kimura S., Golubov A. A., Brinkman A., Koyama K., Watanabe K., Takanashi K., Hiroi M. .  Transport properties of half-metallic Heusler alloy/superconductor junctions III .  Meeting Abstracts of the Physical Society of Japan68.2.3 ( 0 ) 399   2013Transport properties of half-metallic Heusler alloy/superconductor junctions III

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    DOI: 10.11316/jpsgaiyo.68.2.3.0_399_4

  • Goto Junya, Kakimoto Takatoshi, Fujii Shinpei, Koyama Keiichi .  Magnetic and Electronic Structures of Cobalt or Copper Substituted Mn<sub>2</sub>Sb .  MATERIALS TRANSACTIONS54 ( 12 ) 2309 - 2312   2013

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    First-principles total-energy calculations have been performed for the hypothetical case of <i>x</i> = 1 in Mn<sub>2−</sub><i><sub>x</sub></i>X<i><sub>x</sub></i>Sb (X = Co and Cu) for several magnetic states, using the full-potential linearized augmented plane wave method based on the generalized gradient approximation. The calculated total energy indicates that the Co (Cu) atom prefers the site Mn(I) to the site Mn(II) (Mn(II) to Mn(I)). This result of Co is consistent with the available neutron diffraction experiment. For CoMnSb where Co occupies the site Mn(I), the change of lattice constants (<i>a</i> and <i>c</i>) and <i>c</i>/<i>a</i> from AF2 to F is in good agreement with experimental trends. Our results indicate that the optimization of the ratio <i>c</i>/<i>a</i> (lattice distortion) is crucial to determine the most stable magnetic state and that the optimization of the atomic positions of the sites Mn(II) and Sb is also crucial.

    DOI: 10.2320/matertrans.m2013327

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  • Orihashi Hiroki, Hiroi Masahiko, Mitsui Yoshifuru, Takahashi Kohki, Watanabe Kazuo, Matsubayashi Kazuyuki, Uwatoko Yoshiya, Koyama Keiichi .  Magnetic and Structural Properties of Mn<sub>1.8</sub>Co<sub>0.2</sub>Sb under High Magnetic Fields .  MATERIALS TRANSACTIONS54 ( 6 ) 969 - 973   2013

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    Magnetization, electrical resistivity and X-ray diffraction measurements were carried out for Mn<sub>1.8</sub>Co<sub>0.2</sub>Sb with a tetragonal structure in 4.2 ≤ <i>T</i> ≤ 280 K and in field <i>B</i> up to 16 T. For <i>B</i> = 0 T, anisotropic structural deformation occurred at <i>T</i><sub>t</sub> ∼ 140 K for zero-field cooling (ZFC), accompanied by a first-order magnetic transition from the ferrimagnetic (FRI) to antiferromagnetic (AFM) phases. In this deformation, the lattice parameters <i>a</i> and <i>c</i> changed by Δ<i>a</i>/<i>a</i> = +0.15% and by Δ<i>c</i>/<i>c</i> = −0.44%, respectively. By applying magnetic fields of 5 T, <i>T</i><sub>t</sub> decreased to 60 K with thermal hysteresis of 35 K. The two-phase coexistence of the AFM and residual FRI phases was observed even at 10 K for field cooling of 5 T, while a single phase of AFM was confirmed for ZFC. At <i>B</i> = 16 T, the transition did not occurs. In addition, a field-induced structural deformation was observed, accompanied by the metamagnetic transition just below <i>T</i><sub>t</sub>. The obtained results are discussed from a viewpoint on entropy change for the transition.

    DOI: 10.2320/matertrans.m2012415

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  • 西迫裕也, 大久保亮成, 春森浩平, 重田 出, 梅津理恵, 伊藤昌和, 小山佳一, 貝沼亮介, 廣井政彦 .  アンドレーエフ反射法によるハーフメタル型ホイスラー合金Co2MnSiのスピン分極率測定 .  鹿児島大学理学部紀要46   1 - 8   2013アンドレーエフ反射法によるハーフメタル型ホイスラー合金Co2MnSiのスピン分極率測定

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  • Shigeta I., Sakuraba Y., Kimura S., Koyama K., Watanabe K., Takanashi K., Hiroi M. .  Transport and magnetic properties of fully-epitaxial superconducting NbN/half-metallic Heulser alloy Co<sub>2</sub>MnSi bilayer films .  Journal of the Magnetics Society of Japan37 ( 3-2 ) 222 - 226   2013Transport and magnetic properties of fully-epitaxial superconducting NbN/half-metallic Heulser alloy Co<sub>2</sub>MnSi bilayer films

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      Fully-epitaxial NbN/Co<sub>2</sub>MnSi bilayer films were grown on MgO(001) single crystalline substrates by a sputter technique. Structural, electric transport and magnetic properties were investigated for the fabricated films. The resulting NbN/Co<sub>2</sub>MnSi bilayer films show superconducting critical temperature <i>T</i><sub>c</sub> was of 16.0 K and the saturation magnetization <i>M</i><sub>s</sub> at room temperature was of 790 emu/cm<sup>3</sup>. The electric resistivity of the fabricated films was also measured under magnetic fields and the upper critical field <i>B</i><sub>c2</sub> was estimated to be<i>B</i><sub>c2</sub> > 30 T in the case of the applied magnetic field parallel to the MgO(001) single crystalline substrate. In addition, NbN/Co<sub>2</sub>MnSi junctions were made by an electron-beam lithography technique. The enhancement of a zero-bias conductance peak (ZBCP) was observed in differential conductance in the NbN/Co<sub>2</sub>MnSi junctions. The ZBCP disappeared above <i>T</i><sub>c</sub> = 16.0 K of superconducting NbN films.

    DOI: 10.3379/msjmag.1305r007

  • Shigeta I., Sakuraba Y., Molenaar C. G., Beukers J. N., Kimura S., Golubov A. A., Brinkman A., Koyama K., Watanabe K., Takanashi K., Hiroi M. .  27aXA-13 Transport properties of half-metallic Heusler alloy/superconductor junctions II .  Meeting Abstracts of the Physical Society of Japan68.1.3 ( 0 ) 537   201327aXA-13 Transport properties of half-metallic Heusler alloy/superconductor junctions II

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    DOI: 10.11316/jpsgaiyo.68.1.3.0_537_3

  • Mitsui Yoshifuru, Koyama Keiichi, Watanabe Kazuo .  Bi–Mn Binary Phase Diagram in High Magnetic Fields .  MATERIALS TRANSACTIONS54 ( 2 ) 242 - 245   2013

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    To examine magnetic field effects on the Bi–Mn equilibrium phase, a high-magnetic fields differential thermal analysis (HF-DTA) was performed for fields up to 18 T and temperatures ranging from 300 to 753 K. For zero field, the peritectic temperatures <i>T</i><sub>p1</sub> (BiMn<sub>1.08</sub> + Bi-rich liquid → BiMn) and <i>T</i><sub>p2</sub> (αMn + Bi-rich liquid → BiMn<sub>1.08</sub>), and the eutectic temperature <i>T</i><sub>E</sub> (the Bi-rich liquid → Bi solid + BiMn) were determined to be 632, 721 and 538 K, respectively. The Bi–Mn phase diagram at 18 T was obtained, which showed that <i>T</i><sub>p1</sub> increases with increasing magnetic fields at the rate of 2 K T<sup>−1</sup>. Furthermore, the liquidus boundary temperature <i>T</i><sub>liq</sub> between BiMn<sub>1.08</sub> + liquid and Bi-rich liquid was found to increase nonlinearly with increasing magnetic field.

    DOI: 10.2320/matertrans.m2012310

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  • J.A. Monroe, I. Karaman, B. Basaran, W. Ito, R.Y. Umetsu, R. Kainuma, K. Koyama, Y.I. Chumlyakov .  Direct measurement of large reversible magnetic-field-induced strain in Ni-Co-Mn-In metamagnetic shape memory alloys .  Acta Materialia60 ( 20 ) 6883 - 6891   2012.12Direct measurement of large reversible magnetic-field-induced strain in Ni-Co-Mn-In metamagnetic shape memory alloysReviewed

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  • Tasuku Inomata, Michiaki Matsukawa, Daichi Kimura, Yoshiaki Yamato, Satoru Kobayashi, Ramanathan Suryanarayanan, Sigeki Nimori, Keiichi Koyama, Kohki Takahashi, Kazuo Watanabe, Norio Kobayashi .  Suppression of the low-temperature phase-separated state under pressure in (Eu1-xGdx)(0.6)Sr0.4MnO3 (x=0,0.1) .  JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS324 ( 22 ) 3863 - 3869   2012.11Reviewed

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    We have demonstrated the effect of pressure on the steplike metamagnetic transition and its associated magnetostriction in (Eu1-xGdx)(0.6)Sr0.4MnO3 (x=0 and 0.1). The critical field initiating the field induced ferromagnetic transition in both samples is lowered by the applied pressure. The further application of external pressure up to 1.2 GPa on the x=0 parent sample causes a spontaneous ferromagnetic transition with a second-order like character, leading to collapses of the steplike transition and its concomitant lattice striction. These findings indicate a crucial role of the low-temperature phase separated state characterized by a suppressed magnetization upon decreasing temperature. (C) 2012 Elsevier BY. All rights reserved.

    DOI: 10.1016/j.jmmm.2012.06.036

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  • K. Koyama, Y. Mitsui, E.S. Choi, Y. Ikehara, E. Palm, and K. Watanabe .  Controlled Equilibrium State of Ferromagnetic MnBi by High Magnetic Fields .  Proceedings of the 22nd International Workshop on Rare-Earth Permanent Magnets and their Applications, (Nagasaki, 2012)   110 - 113   2012.9Controlled Equilibrium State of Ferromagnetic MnBi by High Magnetic Fields

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  • T. Inomata, M. Matsukawa, D. Kimura, Y. Yamato, S. Kobayashi, R. Suryanarayanan, S. Nimori, K. Koyama, K. Takahashi, K. Watanabe, N. Kobayashi .  Suppression of the low-temperature phase-separated state under pressure in (Eu1-xGdx)0.6Sr0.4MnO3 (x= 0, 0.1) .  J. Magn. Magn. Mater.324   3863 - 3869   2012.7Suppression of the low-temperature phase-separated state under pressure in (Eu1-xGdx)0.6Sr0.4MnO3 (x= 0, 0.1)Reviewed

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  • 折橋広樹、満永大輔、廣井政彦、三井好古、高橋弘紀、渡辺和雄、小山佳一 .  強磁場 X 線回折実験による Mn1.8Co0.2Sb の 磁場中結晶評価 .  日本金属学会誌76 ( 4 ) 246 - 250   2012.4強磁場 X 線回折実験による Mn1.8Co0.2Sb の 磁場中結晶評価Reviewed

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  • S. Ebisu, K. Koyama, T. Horikoshi, M. Kokita, S. Nagata .  Extremely broad hysteresis in the magnetization process of alpha-Dy2S3 single crystal induced by high field cooling .  26TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT26), PTS 1-5400 ( PART 3 )   2012

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    alpha-Dy2S3 possesses orthorhombic crystal structure having two crystallograpically inequivalent Dy sites. Magnetization process of alpha-Dy2S3 single crystal after cooling in the high magnetic field of 18 T has been investigated. The magnetization under the field of 18 T along the a-axis on the cooling process from 150 K shows step-like rises at 70 and 40 K and reaches about 9 mu(B) per one Dy3+ at 1.5 K. This value, which corresponds to 90 % of full saturation moment of Dy3+, is much larger than 6 mu(B) obtained at the same conditions after cooling in no magnetic field (zero-field cooling; ZFC). After cooling to 1.5 K, the magnetization while decreasing field shows abrupt drops at 3.0 and 1.7 T, and then comes to 0 mu(B) at 0 T. Subsequently, while increasing field, the magnetization demonstrates a similar curve to that obtained after ZFC without step-like rise below 13.1 T. At mu H-0 = 13.1 T, the magnetization rises suddenly and agrees with the curve for the decreasing process. This irreversible magnetization process yields extremely broad hysteresis having width of mu(0)Delta H = 11.4 T. Broader hysteresis and narrower one are also observed at 4.2 and 10 K, respectively.

    DOI: 10.1088/1742-6596/400/3/032010

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  • Orihashi Hiroki, Mitsunaga Daisuke, Hiroi Masahiko, Mitsui Yoshifuru, Takahashi Kohki, Watanabe Kazuo, Koyama Keiichi .  X-ray Diffraction Study on Crystal Structure of Mn<sub>1.8</sub>Co<sub>0.2</sub>Sb under High Magnetic Fields .  Journal of the Japan Institute of Metals and Materials76 ( 4 ) 246 - 250   2012

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      Measurements of magnetization, electrical resistivity and high field X-ray powder diffraction (XRD) were carried out for polycrystalline Mn<sub>1.8</sub>Co<sub>0.2</sub>Sb in magnetic fields up to 5 T in 4.2-300 K temperature range, in order to investigate the structural properties affected by magnetic fields. In a zero field, the compound shows the first-order magnetic transition from the ferrimagnetic (FRI) to antiferromagnetic (AFM) states at <i>T</i><sub>t</sub>=145 K with decreasing temperature. By applying magnetic fields of 5 T, <i>T</i><sub>t</sub> decreased to 60 K with thermal hysteresis of 35 K. From the XRD measurements, not only the AFM phase but also the residual FRI phase was confirmed even at 10 K in cooling process under 5 T. Results obtained indicate that the residual FRI phase is kinetically arrested.<br>

    DOI: 10.2320/jinstmet.76.246

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  • Y. Mitsui,K. Koyama,K. Takahashi, and Kazuo Watanabe .  Development of an x-ray diffraction camera used in magnetic fields up to 10 T .  Rev. Sci. Instrum.82   125104(1) - 125104(6)   2011.12Development of an x-ray diffraction camera used in magnetic fields up to 10 TReviewed

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  • 廣井政彦、小山佳一、伊藤昌和、重田 出 .  ヘリウム液化装置 .  鹿児島大学理学部紀要44   27 - 32   2011.12ヘリウム液化装置

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  • Masakazu Ito, Yuji Nagi, Naotoshi Kado, Shinpei Urakawa, Takuro Ogawa, Akihiro Kondo, Keiichi Koyama, Kazuo Watanabe, Koichi Kindo .  Magnetic properties of spinel FeCr2S4 in high magnetic field .  JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS323 ( 24 ) 3290 - 3293   2011.12Reviewed

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    We studied temperature and magnetic field dependence of magnetization, M(T) and M(B), on thiospinel FeCr2S4. We observed a step-like anomaly at T-00 similar to 9 K for M(T) attributed to an orbital order transition in magnetic field 0 &lt;B &lt;= 7 T. Furthermore, also for M(B), the step-like anomaly appears at B-c similar to 5.5 T below T-00. This suggests an existence of a magnetic phase boundary at B-c in T &lt; T-00. Because the anomaly at B-c of M(B) exists in the orbital ordered phase, the spin structure of FeCr2S4 in T &lt; T-00 is strongly coupled with the lattice of the system. (C) 2011 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jmmm.2011.07.041

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  • K. Oikawa, Y. Mitsui, K. Koyama, K. Anzai .  Thermodynamic Assessment of the Bi-Mn System .  MATERIALS TRANSACTIONS52 ( 11 ) 2032 - 2039   2011.11Thermodynamic Assessment of the Bi-Mn SystemReviewed

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  • M. Yamamoto, S. Sekida, T. Fukuda, T. Kakeshita, K. Takahashi,K. Koyama, H. Nojiri .  A new type of FCT martensite phase in single-crystalline Fe(3)Pt Invar alloy .  JOURNAL OF ALLOYS AND COMPOUNDS509 ( 34 ) 8530 - 8533   2011.8A new type of FCT martensite phase in single-crystalline Fe(3)Pt Invar alloyReviewed

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  • Masataka Yamamoto, Sayaka Sekida, Takashi Fukuda, Tomoyuki Kakeshita, Kohki Takahashi, Keiichi Koyama, Hiroyuki Nojiri .  A new type of FCT martensite phase in single-crystalline Fe3Pt Invar alloy .  JOURNAL OF ALLOYS AND COMPOUNDS509 ( 34 ) 8530 - 8533   2011.8Reviewed

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    Martensitic transformation in a highly ordered Fe3Pt has been investigated by magnetization and X-ray diffraction measurements. We confirmed that a new type of face-centered tetragonal (FCT) martensite phase appears below 60 K in Fe3Pt with a degree of order S = 0.88. The tetragonality c/a gradually increases with decreasing temperature, and is approximately 1.005 at 10 K. This is in contrast to the tetragonality c/a &lt; 1 generally observed in the FCT martensite with a degree of order less than 0.8. The spontaneous magnetization increases in association with the transformation. (C) 2011 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jallcom.2011.06.035

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  • H. Kato,K. Koyama, K. Takahashi .  Crystallization of Nd-Co-B nanocomposite ribbons in high magnetic fields .  JOURNAL OF APPLIED PHYSICS109 ( 7 ) 07A726   2011.4Crystallization of Nd-Co-B nanocomposite ribbons in high magnetic fieldsReviewed

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  • Y. Murano, M. Matsukawa, S. Ohuchi, S. Kobayashi, S. Nimori, R. Suryanarayanan, K. Koyama, N. Kobayashi .  Effect of pressure on the magnetic, transport, and thermal-transport properties of the electron-doped manganite CaMn1-xSbxO3 .  Phys. Rev. B 83 ( 5 ) 54437 - -13   2011.2Effect of pressure on the magnetic, transport, and thermal-transport properties of the electron-doped manganite CaMn1-xSbxO3Reviewed

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  • K. Koyama, Y. Mitsui, E.S. Choi, Y. Ikehara, E.C. Palm, K. Watanabe .  Change of the equilibrium state of ferromagnetic MnBi by high magnetic fields .  J. Alloys. Comp.509   L78 - L80   2011.1Change of the equilibrium state of ferromagnetic MnBi by high magnetic fieldsReviewed

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  • R.Y. Umetsu K. Ito, K. Koyama, T. Kanomata, K. Ishida and R. Kainuma, .  Kinetic arrest behavior in martensitic transformation of NiCoMnSn metamagnetic shape memory alloy .  J. Alloys and Comp.509   1389 - 1393   2011.1Kinetic arrest behavior in martensitic transformation of NiCoMnSn metamagnetic shape memory alloyReviewed

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  • M. Ito, Y. Nagi,N. Kado, S. Urakawa,T. Ogawa, A. Kondo,K. Koyama, K. Watanabe, K. Kindo .  Magnetic properties of spinel FeCr(2)S(4) in high magnetic field .  JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS323 ( 24 ) 3290 - 3293   2011Magnetic properties of spinel FeCr(2)S(4) in high magnetic fieldReviewed

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  • Koshi Takenaka, Takashi Shibayama, Kazuko Asano, Keiichi Koyama .  Magnetostructural Correlations in Nitrogen-Deficient Antiperovskite Mn3CuN1-delta .  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN79 ( 7 )   2010.7Magnetostructural Correlations in Nitrogen-Deficient Antiperovskite Mn3CuN1-deltaReviewed

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    Ferromagnetic shape memory effects of antiperovskite Mn3CuN are markedly altered by nitrogen deficiency. The martensitic transformation occurs at a lower temperature than ferromagnetic ordering for nitrogen-deficient Mn3CuN0.8, although they both occur simultaneously for stoichiometric Mn3CuN. In the martensitic phase, Mn3CuN0.8 contracts in a direction parallel to the magnetic field, in contrast to the expansion observed in Mn3CuN, implying that the easy axis is converted from the longer a axis in Mn3CuN to the shorter c axis in Mn3CuN0.8. The operating magnetic field for magnetostriction drastically decreases for Mn3CuN0.8, suggesting a possible supermagnetostriction around the critical compositional region for the easy-axis conversion.

    DOI: 10.1143/JPSJ.79.073706

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  • H Nishihara, Y Furutani, T Wada, T Kanomata, K Kobayashi, R Kainuma, K Ishida, K Koyama, K Watanabe .  Hyperfine coupling constant for 59Co estimated from a high-field susceptibility and high-field NMR shift in ferromagnetic Co2TiGa and Co2VGa .  J. Phys. Conf. Ser.200   32052   2010.1Hyperfine coupling constant for 59Co estimated from a high-field susceptibility and high-field NMR shift in ferromagnetic Co2TiGa and Co2VGaReviewed

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  • K. Takenaka, T. Shibayama, K. Asano and K. Koyama .  Magnetostructural Correlations in Nitrogen-Deficient Antiperovskite Mn3CuN1-δ .  J. Phys. Soc. Jpn.79   73706   2010Magnetostructural Correlations in Nitrogen-Deficient Antiperovskite Mn3CuN1-δReviewed

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  • Y.Mitsui, K. Koyama, W. Ito, R.Y. Umetsu, R. Kainuma, K. Watanabe .  Observation of Reverse Transformation in Metamagnetic Shape Memory Alloy Ni40Co10Mn34Al16 by High-Field X-Ray Diffraction Measurements .  Materials Transactions51   1648 - 1650   2010Observation of Reverse Transformation in Metamagnetic Shape Memory Alloy Ni40Co10Mn34Al16 by High-Field X-Ray Diffraction MeasurementsReviewed

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  • M. Fukuhara, H. Yoshida, K. Koyama, A. Inoue, Y. Miura .  Superconductivity of Ni-Nb-Zr-H Glassy Alloys with Nanoclusters .  J. Nanosci. Nanotech.10   4975 - 4978   2010Superconductivity of Ni-Nb-Zr-H Glassy Alloys with NanoclustersReviewed

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  • K. Watanabe, S. Awaji, K. Koyama, G. Nishijima, K. Takahashi K, and Y. Sasaki .  Tohoku High Magnetic Field Research Activities Using Cryogen-Free Superconducting Magnets .  J. Low Temp. Phys.159   370 - 373   2010Tohoku High Magnetic Field Research Activities Using Cryogen-Free Superconducting MagnetsReviewed

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  • M. Fukuhara, H. Yoshida, K. Koyama, A. Inoue, and Y. Miura .  Electronic transport behaviors of Ni-Nb-Zr-H glassy alloys .  J. Appl. Phys.107   33703   2010Electronic transport behaviors of Ni-Nb-Zr-H glassy alloysReviewed

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  • T. Shigeoka, T. Fujiwara, K. Koyama, K. Watanabe, and Y. Uwatoko .  High Field Metamagnetism of PrRh2Si2 Single Crystal Compound Having Anomalously High NSel Temperature .  J. Low Temp. Phys.159   42 - 45   2010High Field Metamagnetism of PrRh2Si2 Single Crystal Compound Having Anomalously High NSel TemperatureReviewed

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  • A.V. Andreev, E.A. Tereshina, E. Santava, J. Sebek, K. Koyama, and K. Watanabe .  Sublattice contributions to the magnetism of UFe5Al7 and UFe6Al6 .  J. Alloys Comp. 492   52 - 55   2010Sublattice contributions to the magnetism of UFe5Al7 and UFe6Al6Reviewed

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  • X. Xu, W. Ito, R.Y. Umetsu, K. Koyama, R. Kainuma, and K. Ishida .  Kinetic Arrest of Martensitic Transformation in Ni33.0Co13.4Mn39.7Ga13.9 Metamagnetic Shape Memory Alloy .  Mater. Trans.51   469 - 471   2010Kinetic Arrest of Martensitic Transformation in Ni33.0Co13.4Mn39.7Ga13.9 Metamagnetic Shape Memory AlloyReviewed

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  • P.J. Shamberger, A.B. Pakhomov, K. Koyama, F.S. Ohuchi .  Deviation of the magnetization change from the structural phase transition temperature in polycrystalline Ni-Mn-Sn in low magnetic fields .  Scripta Materialia63   1161 - 1164   2010Deviation of the magnetization change from the structural phase transition temperature in polycrystalline Ni-Mn-Sn in low magnetic fieldsReviewed

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  • M. Fukuhara, H. Yoshida, K. Koyama, A. Inoue .  Magnetic-field-induced Coulomb oscillation in Ni-Nb-Zr-H glassy alloys .  Physica B405   3791 - 3794   2010Magnetic-field-induced Coulomb oscillation in Ni-Nb-Zr-H glassy alloysReviewed

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  • M. Yamamoto, T. Fukuda, T. Kakeshita, K. Koyama, H. Nojiri .  Martensitic transformation in invar Fe3Pt with highly ordered state .  Physics Procedia10   117 - 119   2010Reviewed

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    We have investigated martensitic transformation in a highly ordered Fe 3Pt by X-ray diffraction measurements. We found that a new type of FCT martensite phase appears in Fe3Pt with degree of order S = 0.88. In this martensite phase, the tetragonality c/a of the martensite is approximately 1.005 at 10 K, being different from that of so far known FCT martensite phase with c/a &lt
    1.

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  • Masahiko Hiroi, Tsugumi Rokkaku, Kazuhisa Matsuda, Toru Hisamatsu, Iduru Shigeta, Masakazu Ito, Takuo Sakon, Keiichi Koyama, Kazuo Watanabe, Shintaro Nakamura, Tsutomu Nojima, Tomohito Nakano, Lin Chen, Tetsuya Fujiwara, Yoshiya Uwatoko, Hirotaka Manaka, Norio Terada .  Ferromagnetism and spin-glass transitions in the Heusler compounds Ru2-x Fex CrSi .  Physical Review B - Condensed Matter and Materials Physics79 ( 22 )   2009.6Ferromagnetism and spin-glass transitions in the Heusler compounds Ru2-x Fex CrSiReviewed

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    The results of a comprehensive study of the structural, magnetic, and magnetotransport properties of the Heusler compounds Ru2-x Fex CrSi are presented. The Fe-rich compounds (x 1.5) exhibit a usual ferromagnetic transition. The Ru-rich compound (x=0.1) does not show ferromagnetism but exhibits a peak in magnetic susceptibility at TN =30K. Nevertheless, specific-heat measurements show that there is no antiferromagnetic transition at TN nor at any other temperatures. With further decreasing temperature strong irreversible behavior occurs below a temperature Tg. It is proposed that these results can be interpreted as successive spin-glass transitions at TN and Tg. The compounds with intermediate x (=0.3 and 0.5) are found to be ferromagnetic. Both the saturation magnetization and the Curie temperature TC increase with increasing x. However, being different from the Fe-rich compounds, hysteresis of the magnetization is observed and this suggests that the ferromagnetism has glassy character. In lower-temperature range fairly large negative magnetoresistance are observed. These results are suggestive of a magnetically inhomogeneous ferromagnetic state, that is, the formation of ferromagnetic clusters. © 2009 The American Physical Society.

    DOI: 10.1103/PhysRevB.79.224423

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  • A. V. Andreev, K. Koyama, E. A. Tereshina, J. Prokleska, K. Watanabe .  Magnetoelasticity of (Lu(0.8)Ce(0.2))(2)Fe(17) intermetallic compound .  JOURNAL OF ALLOYS AND COMPOUNDS477 ( 1-2 ) 62 - 67   2009.5Reviewed

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    Study of magnetostriction of (Lu(0.8)Ce(0.2))(2)Fe(17) has been performed by two methods, bulk and microscopic: by the capacitor dilatometer on a single crystal grown by the Czochralski method and by the X-ray powder diffraction. The field-induced transition from the antiferromagnetic to the ferromagnetic state is accompanied by the lattice expansion both in the basal plane and along the c-axis of the hexagonal structure. In addition to the spontaneous linear magnetostriction lambda(s)(a) = 0.8 x 10(-3), lambda(s)(c) = 6.8 x 10(-3) along the a and c axes, respectively, and volume effect omega(s) = 8.4 x 10(-3), a comparable field-induced magnetostriction (lambda(a) = 1.3 x 10(-3), lambda(c) = 3.4 x 10(-3), omega = 6.0 x 10(-3)) is observed in a field of 5T applied along the a-axis. (C) 2008 Elsevier B.V. All rights reserved.

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  • H. C. Hsu, F. C. Chou, K. Koyama, K. Watanabe, H. L. Liu .  Spin-phonon coupling in antiferromagnetic Bi2Sr2CoO6+delta: An infrared reflectance study .  PHYSICAL REVIEW B79 ( 15 )   2009.4Reviewed

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    The ab-plane infrared and optical reflectance of single-crystal Bi2Sr2CoO6+delta (0.4 &lt;delta &lt; 0.5) have been measured over a wide frequency range (50-55000 cm(-1)) and at temperatures between 20 and 330 K. The room-temperature infrared spectrum displays an insulating characteristic. The optical gap determined from the infrared conductivity (similar to 0.53 eV) is consistent with thermal activation energy from dc transport measurements. Upon passing through the 265 K antiferromagnetic ordering transition, a softening of the phonon mode near 205 cm(-1) correlates well with the temperature-dependent normalized square of the sublattice magnetization. Furthermore, the magnetic-order-induced splitting of the phonon modes at about 238 and 376 cm(-1) is observed. Additionally, the phonon mode at about 588 cm(-1) exhibits a Fano-type line shape. Since no appreciable structural change was detected at low temperatures in x-ray diffraction studies, all of these observables suggest a complex nature of spin-phonon coupling in this material.

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  • Y. Yamato, M. Matsukawa, Y. Murano, R. Suryanarayanan, S. Nimori, M. Apostu, A. Revcolevschi, K. Koyama, N. Kobayashi .  Colossal electroresistance and colossal magnetoresistive step in paramagnetic insulating phase of single crystalline bilayered manganite (La0.4Pr0.6)(1.2)Sr1.8Mn2O7 .  APPLIED PHYSICS LETTERS94 ( 9 )   2009.3Reviewed

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    We report a significant decrease in the low-temperature resistance induced by the application of an electric current on the ab-plane in the paramagnetic insulating (PMI) state of (La0.4Pr0.6)(1.2)Sr1.8Mn2O7. A colossal electroresistance effect attaining -95% is observed at lower temperatures. A colossal magnetoresistive step appears near 5 T at low temperatures below 10 K, accompanied by an ultrasharp width of the insulator-metal transition. Injection of higher currents to the crystal and magnetic field cooling process cause a disappearance of the steplike transition. These findings have a close relationship with the presence of the short-range charge-ordered clusters pinned within the PMI matrix of the crystal studied.

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  • Yoshifuru Mitsui, Keiichi Koyama, Kazuo Watanabe .  X-ray diffraction measurements in high magnetic fields and at high temperatures .  SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS10 ( 1 )   2009.3X-ray diffraction measurements in high magnetic fields and at high temperaturesReviewed

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    A system was developed measuring x-ray powder diffraction in high magnetic fields up to 5 T and at temperatures from 283 to 473 K. The stability of the temperature is within 1K over 6 h. In order to examine the ability of the system, the high-field x-ray diffraction measurements were carried out for Si and a Ni-based ferromagnetic shape-memory alloy. The results show that the x-ray powder diffraction measurements in high magnetic fields and at high temperatures are useful for materials research.

    DOI: 10.1088/1468-6996/10/1/014612

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  • Y. Furutani, H. Nishihara, T. Kanomata, K. Kobayashi, R. Kainuma, K. Ishida, K. Koyama, K. Watanabe, T. Goto .  Field-induced-moment nuclear coupling for 59Co in a Heusler alloy Co2TiGa .  J. Phys.. Conf. Ser.150   42037 - -4   2009.1Field-induced-moment nuclear coupling for 59Co in a Heusler alloy Co2TiGaReviewed

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  • Yoshifuru Mitsui, Keiichi Koyama, Yuko Nakamori, Shin-ichi Orimo, Kazuo Watanabe .  Magnetic and Structural Phase Transitions in Ferromagnetic MnBi .  JOURNAL OF THE JAPAN INSTITUTE OF METALS73 ( 1 ) 40 - 45   2009.1Magnetic and Structural Phase Transitions in Ferromagnetic MnBiReviewed

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    X-ray powder diffraction, magnetization measurements, and differential thermal analysis (DTA) of polycrystalline MnBi were carried out in zero magnetic field as will as in magnetic fields of up to 14 T and in the temperatures range of 300-773 K, in order to investigate magnetic phase transition. In zero magnetic field, a magnetic phase transition from ferromagnetic to paramagnetic state is exhibited at temperature (T-t) of 628 K, accompanied by decomposition. With increasing magnetic field up to 14 T, T-t increases linearly with the rate of 2 KT-1. A metamagnetic transition between the paramagnetic and field-induced ferromagnetic states was observed just above T-t The exothermic and endothermic peaks were detected in the magnetic field dependence of DTA signals in the interval of 626-623 K, which relates to the metamagnetic transition. The obtained results are discussed on the basis of a mean field theory.

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  • R.Y. Umetsu, W. Ito, K. Ito, K. Koyama, A. Fujita, K. Oikawa, T. Kanomata, R. Kainuma, K. Ishida .  Anomaly in entropy change between parent and martensite phases in the Ni50Mn34In16 Heusler alloy .  Scripta Materialia60   25 - 28   2009Anomaly in entropy change between parent and martensite phases in the Ni50Mn34In16 Heusler alloyReviewed

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  • 三井好古、小山佳一、中森裕子、折茂慎一、渡辺和雄 .  強磁場下における強磁性体MnBiの相転移 .  日本金属学会誌73   40 - 45   2009強磁場下における強磁性体MnBiの相転移Reviewed

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  • 三井好古、小山佳一、渡辺和雄 .  強磁場・高温X線回折測定用試料電気炉の性能評価 .  J. Magn. Soc. Jpn.33   60 - 63   2009強磁場・高温X線回折測定用試料電気炉の性能評価Reviewed

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  • K. Koyama, Y. Mitsui, K. Tahashi and K. Watanabe .  X-ray powder diffraction camera for high-field experiments .  J. Phys.: Conf. Ser.156   12018   2009X-ray powder diffraction camera for high-field experimentsReviewed

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  • K. Koyama, R. Sakakura and K. Watanabe .  Development of an extraction type magnetometer under low temperature and high magnetic fields over 20 T by the hybrid magnet .  J. Phys.: Conf. Ser.156   12019   2009Development of an extraction type magnetometer under low temperature and high magnetic fields over 20 T by the hybrid magnetReviewed

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  • Y. Mitsui, K. Koyama and K. Watanabe .  X-ray diffraction measurements in high magnetic field and at high temperatures .  Sci. Technol. Adv. Mater.10   14612   2009X-ray diffraction measurements in high magnetic field and at high temperaturesReviewed

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  • T. Akiya, H. Kato, M. Sagawa and K. Koyama .  Enhancement of coercivity in Al and Cu added Nd-Fe-B sintered magnets by high field annealing .  IOP Conf. Ser.: Mat. Sci. Eng.1   12034   2009Enhancement of coercivity in Al and Cu added Nd-Fe-B sintered magnets by high field annealingReviewed

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  • Y. Yamato, M. Matsukawa, Y. Murano, R. Suryanarayanan, S. Nimori, M. Apostu, A. Revcolevschi, K. Koyama, N. Kobayashi .  Colossal electroresistance and colossal magnetoresistive step in paramagnetic insulating phase of single crystalline bilayered manganite (La0.4Pr0.6)1.2Sr1.8Mn2O7 .  Appl. Phys. Lett.94   92507   2009Colossal electroresistance and colossal magnetoresistive step in paramagnetic insulating phase of single crystalline bilayered manganite (La0.4Pr0.6)1.2Sr1.8Mn2O7Reviewed

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  • Y. Yamato, M. Matsukawa, S. Nimori, R. Suryanarayanan, Y. Murano, Y. Nakanishi, M. Apostu, A. Revcolevschi, K. Koyama, and N. Kobayashi .  Effect of pressure on Lattice distortion, transport and magnetic properties of Pr-substituted La1.2Sr1.8Mn2O7 bilayered manganite .  J. Phys.: Condens Matter21   486001   2009Effect of pressure on Lattice distortion, transport and magnetic properties of Pr-substituted La1.2Sr1.8Mn2O7 bilayered manganiteReviewed

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  • H.C. Hsu, F.C. Chou, K. Koyama, K. Watanabe and H.L. Liu .  Spin-phonon coupling in antiferromagnetic Bi2Sr2CoO6+δ: An intrared reflectance study .  Phys. Rev. B79   155109   2009Spin-phonon coupling in antiferromagnetic Bi2Sr2CoO6+δ: An intrared reflectance studyReviewed

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  • M. Hiroi M, T. Rokkaku, K. Matsuda, T. Hisamatsu, I. Shigeta, M. Ito, T. Sakon, K. Koyama, K. Watanabe, S. Nakamura, T. Nojima, T. Nakano, L. Chen, T. Fujiwara, Y. Uwatoko, H. Manaka, and N. Terada .  Ferromagnetism and spin-glass transitions in the Heusler compounds Ru2-xFexCrS .  Phys. Rev. B79   224423   2009Ferromagnetism and spin-glass transitions in the Heusler compounds Ru2-xFexCrSReviewed

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  • A.V. Andreev, K. Koyama, E.A. Tereshina, J. Prokleska, and K. Watanabe .  Magnetoelasticity of (Lu0.8Ce0.2)2Fe17 intermetallic compound .  J. Alloys and Compounds477   62 - 67   2009Magnetoelasticity of (Lu0.8Ce0.2)2Fe17 intermetallic compoundReviewed

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  • T Kawamata, N Sugawara, M Uesaka, N Kaneko, T Kajiwara, H Yamane, K Koyama, K Kudo, N Kobayashi, Y Koike .  Single-Crystal Growth of Pb2V3O9 and the Bose-Einstein Condensed State of Triplons Studied by Thermal Conductivity, Specific Heat and Magnetization Measurements .  J. Phys.: Conf. Ser.150   42087   2009Single-Crystal Growth of Pb2V3O9 and the Bose-Einstein Condensed State of Triplons Studied by Thermal Conductivity, Specific Heat and Magnetization MeasurementsReviewed

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  • Y. Yamato, Y. Nakanishi, M. Matsukawa, R. Suryanarayanan, S. Nimori, M. Apostu, A. Revcolevschi, K. Koyama, N. Kobayashi .  Anomalous pressure effect on steplike magnetostriction of (La0.4Pr0.6)(1.2) Sr1.8Mn2O7 bilayered manganese oxide .  25TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT25), PART 4150   2009

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    We report the pressure effect on a steplike magnetostriction of single crystalline (La0.4Pr0.6)(1.2)Sr(1.8)Mb(2)O(7) bilayered manganite, for our understandings of the ultrasharp nature of the field-induced first-order transition from a paramagnetic insulator and to a ferromagnetic metal phase. Application of pressure suppresses a steplike transformation and causes a broad change in the magnetostriction. A delocalization of carriers is promoted with the applied pressure, resulting in the suppressed steplike behaviour. The steplike behaviour observed is closely related to the existence of localized carriers.

    DOI: 10.1088/1742-6596/150/4/042121

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  • S. Ebisu, K. Koyama, H. Omote, S. Nagata .  High field magnetization processes in single crystals of alpha-Tb2S3 and alpha-Dy2S3 .  25TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT25), PART 4150   2009Reviewed

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    Rare earth sesquisulfides alpha-Tb2S3 and alpha-Dy2S3 possess orthorhombic crystal structure having two independent rare earth sites. High field magnetization processes for single crystals of these compounds have been investigated up to mu H-0 = 18 T. Some step-like transitions have been observed in both compounds. The magnetization of alpha-Tb2S3 single crystal under the field along the b-axis at T = 1.4 K shows a steep increase of about 4.5 mu(B), which corresponds to a half of full saturation moment of free Tb3+, at mu H-0 = 2.2 T. It is considered that the reorientation of Tb3+ moments on only one Tb site into a ferromagnetic arrangement occurs. When the magnetic field is perpendicular to the b-axis, one-step transition at mu H-0 = 0.7 T for H parallel to c and two-step transitions at 0.7 and 1.2 T for H parallel to a are observed. As for alpha-Dy2S3, the magnetization curve at T = 1.5 K shows two-step transitions at 1.3 and 1.6 T (H parallel to b), three or four dull steps (H parallel to a or c). The total height of two steps in the M-H curve for H parallel to b corresponds to a half of full Dy3+ moment.

    DOI: 10.1088/1742-6596/150/4/042027

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  • Y. Furutani, H. Nishihara, T. Kanomata, K. Kobayashi, R. Kainuma, K. Ishida, K. Koyama, K. Watanabe, T. Goto .  Field-induced-moment nuclear Coupling for Co-59 in a Heusler alloy Co2TiGa .  25TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT25), PART 4150   2009

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    The positive hyperfine field at Co nucleus in a Heusler alloy Co2TiGa is discussed to be not dominated by the orbital hyperfine field from a quite different point of view from former studies. Field-induced-moment nuclear coupling for Co-59 via spin-orbit interaction on Co atom in Co2TiGa is discussed to be small from the observed high-field shift of the NMR of Co-59 in the ferromagnetic state of only +0.83 % in contrast to the case of CoCl2 center dot 2H(2)O with +29%.

    DOI: 10.1088/1742-6596/150/4/042037

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  • H. Okada, Y. Kusakari, E. Matsuoka, H. Onodera, K. Koyama, K. Watanabe, T. Kanomata .  Transport properties of Heusler compounds Ru2CrGe and Ru2CrSn under high magnetic fields .  25TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT25), PART 4150   2009

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    We have performed the specific heat and the electrical resistivity measurements under high magnetic fields for Heusler compounds Ru2CrGe and Ru2CrSn. We found that the electrical resistivity for Ru2CrGe shows an upturn in the vicinity of 130 K and changes a metallic to a semiconducting-like behavior with decreasing temperature. By applying magnetic field, a negative magnetoresistance was observed below 200 K. On the other hand, the electrical resistivity for Ru2CrSn shows a semimetallic-like behavior. The results of the electrical resistivity in Ru2CrGe suggest that the compound has a gap-like structure in the electronic structure at the Fermi level. Moreover, it was found that another phase transition occurs in Ru2CrGe and Ru2CrSn, in addition to the magnetic transition.

    DOI: 10.1088/1742-6596/150/4/042153

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  • E. G. Gerasimov, N. V. Mushnikov, K. Koyama, T. Kanomata, K. Watanabe .  Positive magnetoresistance and large magnetostriction at first-order antiferro-ferromagnetic phase transitions in RMn(2)Si(2) compounds .  JOURNAL OF PHYSICS-CONDENSED MATTER20 ( 44 )   2008.11Reviewed

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    The magnetostriction and magnetoresistance associated with the field-induced and spontaneous first-order antiferro-ferromagnetic (AF-F) phase transitions have been studied for quasi-single-crystalline samples of La(0.25)Sm(0.75)Mn(2)Si(2), La(0.25)Y(0.75)Mn(2)Si(2) and La(0.27)Y(0.73)Mn(2)Si(2) compounds with natural layered ThCr(2)Si(2)-type structure. It was found that both the spontaneous and field-induced AF-F transitions are accompanied by a large volume magnetostriction Delta V/V approximate to 2 x 10(-3) and anisotropic linear changes of the lattice parameters Delta a/a approximate to 1.6 x 10(-3), Delta c/c approximate to -0.75 x 10(-3). The field-induced AF-F magnetic phase transition has been observed in magnetic fields applied both along the c-axis and in the basal plane, and the magnetostriction value is virtually independent of the direction of applied field. It has been found also that the magnetoresistance is positive in these compounds (the value of the electrical resistance in the ferromagnetic state is higher than that in the antiferromagnetic state) for the fields applied both along the c-axis and in the basal plane. The value of the magnetoresistance observed along the c-axis is 30 times as high as that in the basal plane. The obtained results indicate that the electronic band structure changes are likely responsible for the AF-F magnetic phase transitions observed in the RMn(2)X(2) compounds.

    DOI: 10.1088/0953-8984/20/44/445219

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  • Y. Yamato, M. Matsukawa, T. Kumagai, R. Suryanarayanan, S. Nimori, M. Apostu, A. Revcolevschi, K. Koyama, N. Kobayashi .  Effect of pressure on the steplike magnetostriction of single crystalline bilayered manganite (La(0.4)Pr(0.6))(1.2)Sr(1.8)Mn(2)O(7) .  PHYSICAL REVIEW B78 ( 13 )   2008.10Reviewed

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    We report the effect of pressure on the steplike magnetostriction of single crystalline bilayered manganite (La(0.4)Pr(0.6))(1.2)Sr(1.8)Mn(2)O(7), for our understanding of the ultrasharp nature of the field-induced first-order transition from a paramagnetic insulator to a ferromagnetic metal phase. The application of pressure suppresses a steplike transformation and causes a broad change in the magnetostriction. The injection of an electric current to the crystal also weakens the steplike variation in both the magnetostriction and magnetoresistance. The stabilization of ferromagnetic interaction or the delocalization of charge carriers is promoted with the applied pressure or applied current, resulting in the suppressed steplike behavior. Our findings suggest that the step phenomenon is closely related to the existence of localized carriers such as the short-range charge-orbital-ordered clusters.

    DOI: 10.1103/PhysRevB.78.132411

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  • T. Fujita, H. Okada, K. Koyama, K. Watanabe, S. Maekawa, M. W. Chen .  Unusually Small Electrical Resistance of Three-Dimensional Nanoporous Gold in External Magnetic Fields .  PHYSICAL REVIEW LETTERS101 ( 16 )   2008.10Reviewed

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    We report the electric conductivity of three-dimensional (3D) nanoporous gold at low temperatures and in strong magnetic fields. It was found that topologically disordered 3D nanoporosity leads to extremely low magnetoresistance and anomalous temperature dependence as the characteristic length of nanoporous gold is tuned to be similar to 14 nm. This study underscores the importance of 3D topology of a nanostructure on electronic transport properties and has implications in manipulating electron transport by tailoring 3D nanostructures.

    DOI: 10.1103/PhysRevLett.101.166601

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  • Hiroaki Kato, Takahiro Akiya, Kunihiro Koike, Keiichi Koyama, Masato Sagawa .  Coercivity enhancement induced by high-magnetic-field annealing in sintered Nd-Fe-B magnets .  Proceedings of The 20th Workshop on Rare Earth Permanent Magnets and Applications   2008.9Coercivity enhancement induced by high-magnetic-field annealing in sintered Nd-Fe-B magnetsInvited

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  • A. V. Andreev, E. A. Tereshina, E. Santava, I. Satoh, T. Yamamura, Y. Shiokawa, K. Koyama, K. Watanabe .  Magnetic properties of U-2(Fe1-xNix)(13.6)Si-3.4 single crystals .  JOURNAL OF ALLOYS AND COMPOUNDS461 ( 1-2 ) 6 - 8   2008.8

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    The concentration evolution of crystal structure, magnetic moment and anisotropy constants in U-2(Fe1-xNix)(13.6)Si-3.4 investigated on single crystals grown by the Czochralski method is found to be similar to that in the previously studied U-2(Fe1-xNix)(13.6)Si-3.4 system, only the Ni solubility is limited by x = 0.3 in difference with unlimited Co solubility. (c) 2007 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jallcom.2007.06.086

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  • M. Ohtsuka, J. Sekino, K. Koyama, T. Takagi, K. Itagaki .  Magnetostructural phase transformation and shape memory effect of Fe-added Ni(2)MnGa films .  EUROPEAN PHYSICAL JOURNAL-SPECIAL TOPICS158   173 - 178   2008.5Reviewed

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    The magnetostructural phase transformation and shape memory effect (SME) of Fe-added Ni(2)MnGa films were investigated. The free-standing films were heat-treated at 1073 K for 3.6 ks and constraint-aged (CA) at various conditions (473 similar to 723 K, 0 similar to 14.4 ks) to make the two-way SME. The reversible two-way SME by the temperature change was confirmed through the martensitic transformation (MT) and its reversion. The gradient of strain-temperature curve, the effective recovery strain and the width of thermal hysteresis were dependent on the CA conditions. The magnetic field (MF) induced structural phase transformation was evaluated by an XRD apparatus in high MF up to 5 T. It was confirmed that the martensitic phase was stabilized by the MF. Furthermore, the SME by the MF was observed around MT temperature on cooling process for the CA film. It was concluded that the MF induced SME appeared by the induction of the MT with MF.

    DOI: 10.1140/epjst/e2008-00672-4

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  • K. Koyama, H. Onodera, and K. Watanabe .  Magnetization measurements of DyB2C2 under high pressure and high magnetic fields .  Physica B403   1607 - 1608   2008Magnetization measurements of DyB2C2 under high pressure and high magnetic fieldsReviewed

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  • E.G. Gerasimov, N.V. Nushnikov, K. Koyama, T. Kanomata, and K. Watanabe .  Positive magnetoresistance and large magnetostriction at first-order antiferro-ferromagnetic phase transitions in RMn2Si2 compounds .  J. Phys.: Condens. Matter20   445219   2008Positive magnetoresistance and large magnetostriction at first-order antiferro-ferromagnetic phase transitions in RMn2Si2 compoundsReviewed

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  • A.V. Andreev, E.A. Tereshina, E. Santava, I. Satoh, T. Yamamura, Y. Shiokawa, K. Koyama, K. Watanabe .  Magnetic properties of U2(Fe1-xNix)13.6Si3.4 single crystals .  J. Alloys Comp.461   6 - 8   2008Magnetic properties of U2(Fe1-xNix)13.6Si3.4 single crystalsReviewed

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  • Y. Takahashi, T. Harada, T. Kanomata, K. Koyama, H. Yoshida, T. Kaneko, M. Kataoka .  Magnetoresistance effect of pseudobinary compounds Cr1-xRuxSb2 .  J. Alloys Comp.459   78 - 82   2008Magnetoresistance effect of pseudobinary compounds Cr1-xRuxSb2Reviewed

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  • A.V. Andreev, E.A. Tereshina, E. Santava, K. Koyama, Y. Homma, I. Satoh, T. Yamamura, Y. Shiokawa, K. Watanabe .  Magnetic properties of U2Co17-xSix single crystals .  J. Alloys Comp.450   51 - 57   2008Magnetic properties of U2Co17-xSix single crystalsReviewed

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  • T. Sakon, S. Saito, K. Koyama, S. Awaji, I. Sato, T. Nojima, K. Watanabe, M. Motokawa, N.K. Sato .  Magnetic anisotropy study of UGe2 in a static high magnetic field .  J. Phys.: Conf. Ser. 51   255 - 258   2008Magnetic anisotropy study of UGe2 in a static high magnetic fieldReviewed

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  • T. Shigeoka, N. Kimura, K. Koyama and K. Watanabe .  High field magnetization of TbCu2Si2 single crystal compound .  J. Phys.: Conf. Ser51   83 - 86   2008High field magnetization of TbCu2Si2 single crystal compoundReviewed

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  • Y. Makihara, H. Fujii, T. Fujiwara, K. Watanabe, K. Takahashi, K. Koyama and M. Motokawa .  Magneto-volume effect in the ground and field induced states of Ce2Fe17 .  Physica B329-333   663 - 664   2008Magneto-volume effect in the ground and field induced states of Ce2Fe17Reviewed

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  • T. Fujiwara, H. Fujii, Y. Uwatoko, K. Koyama, M. Motokawa and T. Shigeoka .  Dramatic change of the magnetic characteristics in YbMn2Ge2 under high pressures .  Acta Phys. Pol. B (Sp. Iss.)34   1541 - 1544   2008Dramatic change of the magnetic characteristics in YbMn2Ge2 under high pressuresReviewed

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  • K. Koyama, T. Goto, T. Kanomata, R. Note and Y. Takahashi .  Nonlinear magnetization process of single-crystalline FeSi .  J. Phys. Soc. Jpn.69   219 - 224   2008Nonlinear magnetization process of single-crystalline FeSiReviewed

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  • H. Okada, K. Koyama, M. Nakatake, K. Shimada, H. Namatame, M. Taniguchi, and K. Watanabe .  Photoemission spectroscopy of spinel-type CuV2S4 single crystal .  J. Phys. Soc. Jpn77   114711   2008Photoemission spectroscopy of spinel-type CuV2S4 single crystalReviewed

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  • H. Okada, K. Koyama, M. Hedo, Y. Uwatoko, and K. Watanabe .  Pressure-induced metal-insulator transition in spinel compound CuV2S4 .  Phsica B403   1612 - 1613   2008Pressure-induced metal-insulator transition in spinel compound CuV2S4Reviewed

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  • Y. Yamato M. Matsukawa, T. Kumagai, R. Suryanarayanan, S. Nimori, M. Apostu, A. Revcolevschi, K. Koyama, and N. Kobayashi .  Effect of pressure on the steplike magnetostriction of single crystalline bilayered manganite (La0.4Pr0.6)1.2Sr1.8Mn2O7 .  Phys. Rev. B78   132411   2008Effect of pressure on the steplike magnetostriction of single crystalline bilayered manganite (La0.4Pr0.6)1.2Sr1.8Mn2O7Reviewed

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  • W. Ito, K. Ito, R.Y. Umetsu, R. Kainuma, K. Koyama, K. Watanabe, A. Fujita, K. Oikawa, K. Ishida, T. Kanomata .  Kinetic arrest of martensitic transformation in the NiCoMnIn metamagnetic shape memory alloy .  Appl. Phys. Lett.92   21908   2008Kinetic arrest of martensitic transformation in the NiCoMnIn metamagnetic shape memory alloyReviewed

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  • K. Takahashi, K. Koyama, and K. Watanabe .  100 mm wide bore cryocooled hybrid magnet for a high field X-ray diffractometer .  IEEE trans. Apply. Superconductivity18   536 - 539   2008100 mm wide bore cryocooled hybrid magnet for a high field X-ray diffractometerReviewed

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  • T. Fujita, H. Okada, K. Koyama, K. Watanabe, S. Maekawa and M.W. Chen .  Unusual Small Electrical Resistance of Three-Dimensional Nanoporous Gold in External Magnetic Fields .  Phys. Rev. Lett.101   166601   2008Unusual Small Electrical Resistance of Three-Dimensional Nanoporous Gold in External Magnetic FieldsReviewed

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  • K. Koyama, Y. Mitsui and K. Watanabe .  Magnetic and structural phase transitions of MnBi under high magnetic fields .  Sci. Technol. Adv. Mater.9   24204   2008Magnetic and structural phase transitions of MnBi under high magnetic fieldsReviewed

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  • M. Ohtsuka, J. Sekino, K. Koyama, T. Takagi, and K. Itagaki .  Magnetostructural phase transformation and shape memory effect of Fe-added Ni2MnGa films .  Eur. Phys. J. Special Topics158   173 - 178   2008Magnetostructural phase transformation and shape memory effect of Fe-added Ni2MnGa filmsReviewed

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  • K. Asano, K. Koyama, and K. Takenaka .  Magnetostriction in Mn3CuN .  Appl. Phys. Lett.92   161909   2008Magnetostriction in Mn3CuNReviewed

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  • H. Okada, K. Koyama, K. Watanabe, Y. Kusakari, T. Kanomata, and H. Nishihara .  Magnetic properties of Heusler compounds Ru2CrGe and Ru2CrSn .  Appl. Phys. Lett. 92   62502   2008Magnetic properties of Heusler compounds Ru2CrGe and Ru2CrSnReviewed

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  • E.A. Tereshina, A.V. Andreev, K. Koyama, K. Watanabe .  Magnetostriction at the Metamagnetic Phase Transition in (Lu0.8Ce0.2)2Fe17 .  WDS’08 Proceedings of Contributed papers, Part III,   101 - 106   2008Magnetostriction at the Metamagnetic Phase Transition in (Lu0.8Ce0.2)2Fe17

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  • Makoto Yoshida, Yumiko Kitano, Yuji Inagaki, Takahiro Sakurai, Motoi Kimata, Susumu Okubo, Hitoshi Ohta, Keiichi Koyama, Mitsuhiro Motokawa, Takayuki Asano, Yoshitami Ajiro .  Observation of direct transitions in the ferromagnetic and antiferromagnetic dimer system (CH3)(2)NH2CUCl3 by high-field ESR .  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN76 ( 11 )   2007.11Observation of direct transitions in the ferromagnetic and antiferromagnetic dimer system (CH3)(2)NH2CUCl3 by high-field ESRReviewed

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    High-field electron spin resonance (ESR) measurements of single crystals of (CH3)(2)NH2CuCl3 (DMACuCl(3)) have been performed in the frequency range of 50 to 550 GHz in the paramagnetic region. In addition to the electron paramagnetic resonance, we have observed four ESR modes omega(1), omega(2), omega(3), and omega(4). The modes omega(2) and omega(3) have a frequency gap of 325 GHz (15.6 K), while the mode omega(1) has a gap of 420 GHz (20 K) at 0 T. The modes omega(2) and omega(3) are attributed to the transitions between the singlet and the triplet of the antiferromagnetic (AF) dimer. We found that the large spin-gap for the AF dimer still remains at the critical field B-c2 = 3.5 T determined by magnetization and specific heat measurements.

    DOI: 10.1143/JPSJ.76.113704

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  • K. Hachitani, H. Amanuma, H. Fukazawa, Y. Kohori, I. Watanabe, K. Koyama, K. Kumagai, C. Sekine, I. Shirotani .  Sm-based filled skutterudite phosphides SmT4P12 (T = fe, ru, os) studied by P-31-NMR and mu SR .  JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS68 ( 11 ) 2080 - 2083   2007.11

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    The Sm-based filled skutterudite phosphides SmT4P12 (T = Fe, Ru, Os) have been studied by P-31-NMR (nuclear magnetic resonance) and mu SR (muon spin relaxation). The ferromagnetic order and the heavy fermion behavior in SmFe4P12 and the anti ferromagnetic order in SmOs4P12 were confirmed by P-31-NMR and mu SR. In SmRu4P12, a successive anomaly around the metal-insulator transition temperature and around the Neel temperature was observed by 31P-NMR in high applied magnetic fields. The mu SR results of SmRu4P12 indicate the magnetic order below the metal-insulator transition temperature, which supports the existence of the octupolar order in SmRu4P12. (c) 2007 Published by Elsevier Ltd.

    DOI: 10.1016/j.jpcs.2007.08.033

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  • E. A. Tereshina, A. V. Andreev, K. Koyama, Y. Shiokawa, I. Satoh, K. Watanabe .  Magnetic anisotropy and spin reorientation in U2Co15Si2 .  JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS316 ( 2 ) E515 - E518   2007.9Reviewed

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    Field and temperature dependencies of the magnetization measured along the principal axes of a U2Co15Si2 single crystal show that this compound is a ferromagnet with a spontaneous magnetic moment of 14.8 mu(B) per formula unit (at 4.2 K), located in the basal plane of the hexagonal crystal structure. A strong easy-plane magnetic anisotropy (K-1 = -0.97 MJ m(-3) at 4.2 K) is attributed to the U sublattice because Lu2Co15Si2 exhibits easy-axis anisotropy with K-1 = 0.42 MJ m(-3). The easy-plane anisotropy of U2Co15Si2 transforms to a cone of easy axes above 270 K. The magnetization vector approaches the c-axis at 350 K, and the compound has easy c-axis anisotropy up to the Curie temperature T-C = 601 K. (C) 2007 Published by Elsevier B.V.

    DOI: 10.1016/j.jmmm.2007.03.006

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  • A. V. Andreev, K. Koyama, N. V. Mushnikov, V. Sechovsky, Y. Shiokawa, I. Satoh, K. Watanabe .  Interplay between effects of external pressure and dilution of the U sublattice in UCoAl-based materials .  JOURNAL OF ALLOYS AND COMPOUNDS441 ( 1-2 ) 33 - 38   2007.8Reviewed

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    Substitution of Y for U in the itinerant 5f-electron metamagnet, UCoAl, transforms the system to a ferromagnetic state. Application of external hydrostatic pressure above 0.3 GPa suppresses the ferromagnetism and restores the "UCoAl-type" metamagnetism back. However, the metamagnetic transition becomes of the second order instead of the first order one in parent UCoAl. This is attributed to enhancement of fluctuations of the U magnetic moment upon dilution of the U sublattice. (C) 2006 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jallcom.2006.09.111

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  • Tetsuya Onogi, Keiichi Koyama, Kazuo Watanabe .  Magnetic properties of MnBi in high magnetic fields and high temperature .  JOURNAL OF THE JAPAN INSTITUTE OF METALS71 ( 6 ) 489 - 493   2007.6Magnetic properties of MnBi in high magnetic fields and high temperatureReviewed

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    Magnetization measurements of polycrystalline MnBi were carried out in magnetic fields up to 10 T and in the temperature range from 300 to 773 K, in order to clarify the magnetic properties under high magnetic fields and high temperature. The magnetic phase transition temperature (T-c) at a zero magnetic field is 633 K, which almost linearly increases by 2.3 KT-1 with increasing fields up to 10 T. Furthermore, a metamagnetic transition was observed just above T, indicating that the phase transition is first order. The magnetic entropy change is estimated to be 14 J kg(-1) K-1 for 2 T at T-c using Clausius-Clapayron's equation, which is almost constant for magnetic fields up to 10 T.

    DOI: 10.2320/jinstmet.71.489

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  • M. Matsukawa, Y. Yamato, T. Kumagai, A. Tamura, R. Suryanarayanan, S. Nimori, M. Apostu, A. Revcolevschi, K. Koyama, N. Kobayashi .  Steplike lattice deformation of single crystalline (La0.4Pr0.6)(1.2)Sr1.8Mn2O7 bilayered manganite .  PHYSICAL REVIEW LETTERS98 ( 26 )   2007.6

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    We report a steplike lattice transformation of single crystalline (La0.4Pr0.6)(1.2)Sr1.8Mn2O7 bilayered manganite accompanied by both magnetization and magnetoresistive jumps, and examine the ultrasharp nature of the field-induced first-order transition from a paramagnetic insulator to a ferromagnetic metal phase accompanied by a huge decrease in resistance. Our findings support that the abrupt magnetostriction is closely related to an orbital frustration existing in the inhomogeneous paramagnetic insulating phase rather than a martensitic scenario between competing two phases.

    DOI: 10.1103/PhysRevLett.98.267204

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  • T. Sakon, S. Saito, K. Koyama, S. Awaji, I. Sato, T. Nojima, K. Watanabe, N. K. Sato .  Experimental investigation of giant magnetocrystalline anisotropy of UGe2 .  PHYSICA SCRIPTA75 ( 4 ) 546 - 550   2007.4

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    UGe2 is a ferromagnetic heavy-fermion (HF) superconductor, which provides superconductivity under pressure in the range of 1.0 to 1.5 GPa. In this paper, we conducted detailed magnetization experiments up to 27 T and at atmospheric pressure. Magnetization along the a-axis indicates typical ferromagnetic property. On the other hand, magnetization along the b-axis is quite a bit smaller than that of the easy a-axis. The magnetocrystalline anisotropy constant is the same as the rare earth ferromagnet Nd2Fe17, which indicates that UGe2 is a highly anisotropic ferromagnet.

    DOI: 10.1088/0031-8949/75/4/030

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  • S. V. Demishev, A. V. Semeno, A. A. Pronin, N. E. Sluchanko, N. A. Samarin, H. Ohta, S. Okubo, M. Kimata, K. Koyama, M. Motokawa, A. V. Kuznetsov .  Quantum criticality and collective effects in low-dimensional magnet CuGeO3 : Fe probed by high frequency EPR .  JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM20 ( 2 ) 105 - 108   2007.2

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    For CuGeO3 single crystals doped with 1% of Fe, the quantum critical behavior in a wide temperature range 1-40 K is reported. The critical exponents for susceptibility along different crystallographic axes are determined: alpha = 0.34 (B parallel to a and B parallel to c) and alpha = 0.31 (B parallel to b). The description of the temperature dependencies of the line width and g-factor could be obtained in the Oshikawa-Affleck theory assuming that staggered component of the magnetic moment is located predominantly along b-axis. Possible arguments favoring the competition between effects of the staggered field and antiferromagnetic ordering are provided.

    DOI: 10.1007/s10948-006-0214-3

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  • M. Yoshida, Y. Kitano, Y. Inagaki, T. Sakurai, M. Kimata, S. Okubo, H. Ohta, K. Koyama, M. Motokawa, T. Asano, and Y. Ajiro .  Observation of direct transitions in the ferromagnetic and antiferromagnetic dimmer system (CH3)2NH2CuCl3 by high-field ESR .  J. Phys. Soc. Jpn76   113704   2007.1Observation of direct transitions in the ferromagnetic and antiferromagnetic dimmer system (CH3)2NH2CuCl3 by high-field ESRReviewed

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  • M. Matsukawa, A. Tamura, S. Nimori, R. Suryanarayanan, T. Kumagai, Y. Nakanishi, M. Apostu, A. Revcolevschi, K. Koyama, N. Kobayashi .  Anomalous pressure effect on the remanent lattice striction of a (La,Pr)(1.2)Sr1.8Mn2O7 bilayered manganite single crystal .  PHYSICAL REVIEW B75 ( 1 )   2007.1

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    We have studied the pressure effect on magnetostriction, both in the ab plane and along the c axis of a (La, Pr)(1.2)Sr1.8Mn2O7 bilayered manganite single crystal over the temperature region where the field-induced ferromagnetic metal (FMM) transition takes place. For comparison, we have also examined the pressure dependence of magnetization curves at the corresponding temperatures. The applied pressure reduces the critical field of the FMM transition and it enhances the remanent magnetostriction. An anomalous pressure effect on the remanent lattice relaxation is observed and is similar to the pressure effect on the remanent magnetization along the c axis. These findings are understood from the viewpoint that the double-exchange interaction-driven FMM state is strengthened by the application of pressure.

    DOI: 10.1103/PhysRevB.75.014427

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  • Evgeniya A. Tereshina, Hajime Yoshida, Alexander V. Andreev, Irina S. Tereshina, Keiichi Koyama, Takeshi Kanomata .  Magnetism of a Lu2Fe17H Single Crystal under Pressure .  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN76   82 - 83   2007.1Reviewed

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    Lu2Fe17 is a ferromagnet below T-C similar to 140 K and antiferromagnet up to T-N = 275 K. Hydrogen absorption leads to a stabilization of the ferromagnetism over the whole range of magnetic order and to an increase of the ordering temperature up to T-C=354 K in Lu2Fe17H. The external pressure compensates the lattice expansion upon hydrogenation, and a reentrance of antiferromagnetism is observed.

    DOI: 10.1143/JPSJS.76SA.82

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  • M. Kimata, Y. Oshima, H. Ohta, K. Koyama, M. Motokawa, H. M. Yamamoto, R. Kato .  Low-temperature Fermi surface of the organic conductor beta(')-(BEDT-TTF)(TCNQ)((1-x))(F1-TCNQ)(x) (x=0,0.05) from magnetooptical measurements .  PHYSICAL REVIEW B75 ( 4 )   2007.1

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    Magnetooptical measurements have been performed on the organic conductor beta(')-(BEDT-TTF)(TCNQ) (x=0 salt), and a related compound, beta(')-(BEDT-TTF)(TCNQ)(0.95)(F1-TCNQ)(0.05) (x=0.05 salt), to investigate their low-temperature Fermi surfaces (FSs). Although the room-temperature FS of both salts can be considered the same, our results indicate that the low-temperature FSs are completely different from each other. In the x=0 salt, the low-temperature FS consists of two very anisotropic quasi-two-dimensional (Q2D) FSs. Cross-sectional areas of anisotropic Q2D-FSs are very small, and correspond to 1-2 % of the first Brillouin zone at room temperature. On the other hand, in the x=0.05 salt, only a pair of quasi-one-dimensional FSs exist at low temperature. Compared with the band calculation of x=0 salt, this Q1D-FS originates from the BEDT-TTF conducting layers. This result indicates that the two hump-like anomalies in the temperature dependence of resistivity at 80 and 20 K, which are observed only in the x=0 salt, are related to the nesting of BEDT-TTF Q1D-FS. Hence, it is considered that anisotropic Q2D-FS pockets observed in the x=0 salt are generated by the imperfect nesting of Q1D-FS, and the density wave state may be formed in the x=0 salt at low temperatures.

    DOI: 10.1103/PhysRevB.75.045126

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  • Alexander V. Andreev, Keiichi Koyama, Nikolai V. Mushnikov, Vladimir Sechovsky, Yoshinobu Shiokawa, Isamu Satoh, Kazuo Watanabe .  Transition from Ferromagnetism to Metamagnetism under Pressure in a U0.94Y0.06CoAl Single Crystal .  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN76   43 - 46   2007.1Reviewed

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    Substitution of Y for U in the itinerant 5f-electron metamagnet UCoAl transforms the system to a ferromagnetic ground state. Application of external hydrostatic pressure above 0.3 GPa suppresses the ferromagnetism and restores the "UCoAl-type" metamagnetism. However, the metamagnetic transition becomes of the second-order type instead of the first-order one for the parent UCoAl.

    DOI: 10.1143/JPSJS.76SA.43

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  • K. Koyama, S. Miura, H. Okada, T. Shigeoka, K. Watanabe .  Magnetic entropy changes of SmMn2Ge2 under high pressure .  Mater. Trans.48   451 - 454   2007Magnetic entropy changes of SmMn2Ge2 under high pressureReviewed

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  • K. Hachitani, H. Amanuma, H. Fukazawa, Y. Kohori I. Watanabe, K. Koyama, K. Kumagai, C. Sekine and I. Shirotani .  Sm-based filled Skutterudite phosphides SmT4P12 (T=Fe, Ru, Os) studied by 31P-NMR and μSR .  J. Phys. Chem. Solid68   2080 - 2083   2007Sm-based filled Skutterudite phosphides SmT4P12 (T=Fe, Ru, Os) studied by 31P-NMR and μSRReviewed

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  • M. Matsukawa, Y. Yamato, T. Kumagai, A. Tamura, R. Suryanarayanan, S. Nimori, M. Apostu, A. Recolevschi, K. Koyama, and N. Kobayashi .  Steplike lattice deformation of single crystalline (La0.4Pr0.6)1.2Sr1.8Mn2O7 bilayered Manganite .  Phys. Rev. Lett.98   267204   2007Steplike lattice deformation of single crystalline (La0.4Pr0.6)1.2Sr1.8Mn2O7 bilayered ManganiteReviewed

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  • E.A. Tereshina, A.V. Andreev, K. Koyama, Y. Shiokawa, I. Satoh, and K. Watanabe .  Magnetic anisotropy and spin reorientation U2Co15Si2 .  J. Magn. Magn. Mater316   e515 - e518   2007Magnetic anisotropy and spin reorientation U2Co15Si2Reviewed

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  • A.V. Andreev, E.A. Tereshina, E. Santava, K. Koyama, Y. Homma, I. Satoh, T. Yamamura, Y. Shiokawa, K. Watanabe .  Crystal structure and magnetic properties of U2Co17-xSix single crystals .  J. Magn. Magn. Mater.310   e598 - e600   2007Crystal structure and magnetic properties of U2Co17-xSix single crystalsReviewed

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  • A. Himori, M. Tanaka, K. Koyama, K. Watanabe and T. Shigeoka .  Magnetic behavior of TbRh2Si2 single crystal .  J. Magn. Magn. Mater.310   1770 - 1772   2007Magnetic behavior of TbRh2Si2 single crystalReviewed

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  • T. Sakon, S. Saito, K. Koyama, S. Awaji, I. Sato, T. Nojima, K. Watanabe and N.K. Sato .  Experimental investigation of giant magnetocrystaline anisotropy of UGe2 .  Phys. Scr.75   546 - 550   2007Experimental investigation of giant magnetocrystaline anisotropy of UGe2Reviewed

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  • M. Matsukawa, A. Tamura, S. Nimmori, R. Suryanarayanan, T. Kumagai, Y. Nakanishi, M. Apostu, A. Revcolevschi, K. Koyama, and N. Kobayashi .  Anomalous pressure effect on the remanent lattice striction of a (La, Pr)1.2Sr1.8Mn2O7 bilayered manganite single crystal .  Phys. Rev. B75   14427   2007Anomalous pressure effect on the remanent lattice striction of a (La, Pr)1.2Sr1.8Mn2O7 bilayered manganite single crystalReviewed

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  • A.V. Andreev, K. Koyama, N.M. Mushnikov, V. Sechovsky, Y. Shiokawa, I. Satoh, and K. Watanabe .  Interplay between effects of external pressure and dilution of the U-sublattice in UCoAl-base materials .  J. Alloys Comp.441   33 - 38   2007Interplay between effects of external pressure and dilution of the U-sublattice in UCoAl-base materialsReviewed

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  • O. Tegus, K. Koyama, J.L. Her, K. Watanabe, E. Bruck, K.H.J. Buschow, F.R. de Boer .  X-ray diffraction on MnFeP0.46As0.54 in a magnetic field .  Physica B392   151 - 153   2007X-ray diffraction on MnFeP0.46As0.54 in a magnetic fieldReviewed

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  • K. Wang, T. Fujita, M.W. Chen, T.G. Nieh, H. Okada, K. Koyama, W. Zhang and A. Inoue .  Electrical conductivity of a bulk metallic glass composite .  Appl. Phys. Lett.91   154101   2007Electrical conductivity of a bulk metallic glass compositeReviewed

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  • H. Kato, T. Akiya, M. Sagawa, K. Koyama and T. Miyazaki .  Effect of high magnetic field on the coercivity in sintered Nd-Fe-B magnets .  J. Magn. Magn. Matter.310   2596 - 2598   2007Effect of high magnetic field on the coercivity in sintered Nd-Fe-B magnetsReviewed

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  • K. Koyama, T. Onogi, Y. Mitsui, Y. Nakamoi, S. Orimo, and K. Watanabe .  Magnetic phase transition of MnBi under high magnetic fields and high temperature .  Mater. Trans.48   2414 - 2418   2007Magnetic phase transition of MnBi under high magnetic fields and high temperatureReviewed

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  • 小野木哲也、小山佳一、渡辺和雄 .  一次相転移物質MnBi の高温・強磁場磁気特性 .  日本金属学会誌71   489 - 493   2007一次相転移物質MnBi の高温・強磁場磁気特性Reviewed

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  • K. Koyama, T. Iagarashi, H. Okada, K. Watanabe, T. Kanomata, R. Kainuma, W. Ito, K. Oikawa, K. Ishida .  Magnetic and thermoelectric properties of Ni50Mn36Sn14 in high magnetic fields .  J. Magn. Magn. Mater.310   e994 - e995   2007Magnetic and thermoelectric properties of Ni50Mn36Sn14 in high magnetic fieldsReviewed

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  • M. Kimata, Y. Oshima, H. Ohta, K. Koyama, M. Motokawa, H.M. Yamamoto, and R. Kato .  Low-temperature Fermi surface of the organic conductor β”-(BEDT-TTF)(TCNQ)(1-x)(F1-TCNQ)x (x=0, 0.05) from magnetooptical measurements .  Phys. Rev. B75   45126   2007Low-temperature Fermi surface of the organic conductor β”-(BEDT-TTF)(TCNQ)(1-x)(F1-TCNQ)x (x=0, 0.05) from magnetooptical measurementsReviewed

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  • Kenichi Hachitani, Hideaki Amanuma, Hideto Fukazawa, Yoh Kohori, Keiichi Koyama, Ken-ichi Kumagai, Chihiro Sekine, Ichimin Shirotani .  Appearance of successive phase transition in SmRU4P12 under high magnetic fields probed by P-31 nuclear magnetic resonance .  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN75 ( 12 )   2006.12Appearance of successive phase transition in SmRU4P12 under high magnetic fields probed by P-31 nuclear magnetic resonanceReviewed

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    The P-31-NMR (nuclear magnetic resonance) measurements of the filled skutterudite SmRu4P12 have been carried out in several applied magnetic fields. The line width of the P-31-NMR spectrum rapidly increases below the metal-insulator transition temperature T-MI, which indicates the appearance of an internal field below the temperature. Though no distinct anomaly was observed below T-MI in low fields, a complicated structure was observed between the Neel temperature T-N and T-MI (T-N &lt; T-MI) above 70 kOe. The spin-lattice relaxation rate l/T-1 is almost independent of temperature above T-MI, and rapidly decreases below T-MI. The l/(T1) in low fields decreases monotonously, whereas the strong suppression of l/(T1) occurs between T-N and T-MI above 70 kOe. The structure of the spectra and the suppression of l/T-1 become apparent with increasing field.

    DOI: 10.1143/JPSJ.75.124712

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  • J Prchal, H Kitazawa, T Furubayashi, P Javorsky, K Koyama, Sechovsky, V .  Low-temperature structural study of the TbPd1-xNixAl series .  PHYSICA B-CONDENSED MATTER378-80   1102 - 1104   2006.5

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    A discontinuity in the temperature dependence of the lattice parameters while preserving the crystal symmetry was observed for TbPdAl, TbNiAl and TbPd0.9Ni0.1Al. We associate this result with the previously reported step-like change in the concentration dependence of lattice parameters in RE(Ni1-xCux)Al pseudo-ternary compounds. Our results corroborate the scenario for the RTX compounds with the ZrNiAl-type structure based on existence of a narrow interval of forbidden c/a values. For TbPdAl, TbNiAl and TbPd0.9Ni0.1Al we observed also a certain temperature interval of coexistence of two ZrNiAl-type phases characterized by two distinctly different c/a values. (c) 2006 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physb.2006.01.437

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  • K Yagasaki, S Notsu, Y Takaesu, T Nakama, E Sakai, K Koyama, K Watanabe, AT Burkov .  X-Ray diffraction on rare earth-3d Laves phase compound ErCo2 in magnetic field .  PHYSICA B-CONDENSED MATTER378-80   1089 - 1090   2006.5

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    X-Ray powder diffraction method is used to investigate the effect of magnetic ordering and external magnetic field on crystal structure of Laves phase intermetallic compound ErCo2. The diffraction patterns were recorded at temperatures from 300 K down to 8.5 K in magnetic field up to 5 T. Distortion of the room-temperature cubic structure was found in magnetically ordered state below 32 K. The symmetry at low temperature is rhombohedral in agreement with literature results. Or lower symmetry than it. However the symmetry of the unit cell increases to cubic in external magnetic field of 5 T. (c) 2006 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physb.2006.01.514

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  • Kazuo Watanabe, Asaya Fujita, Keiichi Koyama .  Special issue on Research on New Magnetic Properties and Applications to Materials Science in Itinerant-Electron Systems - Preface .  MATERIALS TRANSACTIONS47 ( 3 ) 455 - 455   2006.3Special issue on Research on New Magnetic Properties and Applications to Materials Science in Itinerant-Electron Systems - PrefaceReviewed

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    DOI: 10.1113/jphysiol.2006.114231

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  • M. Kimata, Y. Oshima, K. Koyama, H. Ohta, M. Motokawa, H. Nishikawa, K. Kikuchi, I. Ikemoto .  Detailed fermi surface topology of the quasi-one-dimensional conductor (DMET)(2)I-3 .  JOURNAL OF LOW TEMPERATURE PHYSICS142 ( 3-4 ) 523 - 526   2006.2

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    The detailed topology of the Fermi surface of the quasi-one-dimensional conductor (DMET)(2)I-3 was investigated by the magnetooptical measurements. A pair of planar Fermi surface which has higher corrugations of Fourier components was observed. This result seems to suggest that the metallic state of this salt is stabilized by the higher corrugations of the Fermi surface.

    DOI: 10.1007/s10909-006-9159-y

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  • H Okada, K Koyama, M Yamada, T Goto, Y Makihara, H Fujii, K Watanabe .  Magnetic properties of Ce(Fe1-xCox)(2) under high pressure .  JOURNAL OF ALLOYS AND COMPOUNDS408   144 - 146   2006.2

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    We have studied the magnetic properties of Ce(Fe1 xCox)(2) with x = 0 and 0.05 by magnetization measurements under high pressure. In both compound, the remarkable suppression of the magnetization is observed below T* in the ferromagnetic (FM) state under 1.2 GPa. T* shifts to lower temperature with increasing the magnetic field, and the extrapolated value to the zero magnetic field is estimated to be 95 and 123 K. These high pressure and magnetic field effects are probably due to the enhancement and the suppression of the AFM spin fluctuation, respectively. (c) 2005 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jallcom.2005.04.057

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  • H Kato, H Kubota, K Koyama, T Miyazaki .  Fabrication of SmFe12/alpha-Fe thin films as anisotropic nanocomposite magnet .  JOURNAL OF ALLOYS AND COMPOUNDS408   1368 - 1372   2006.2

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    A series of nanocomposite thin films, composed of alpha-Fe and c-axis oriented SmFe12 phases, has been synthesized by rf magnetron sputtering onto heated glass substrates. The volume fraction of alpha-Fe, V-Fe, in the obtained films ranges from 5% to 85%. According to the Rietveld analysis of X-ray diffraction patterns, the c-axis of each SmFe12 grain was estimated to locate within a cone with its symmetry axis being normal to the film plane and with the cone angle of 7 degrees. For samples with VFe &lt; 30%, the demagnetization curves with fields applied normal to the film plane have exhibited a good squareness. In small VF, films, the coercivity H, increased with increasing V-Fe took a maximum for VFe similar to 25%, and then decreased. In the reference system of randomly aligned SmFe12/alpha-Fe films, on the other hand, we confirmed that H-c decreased monotonically with increasing V-Fe. (c) 2005 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jallcom.2005.04.108

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  • H. Okada, K. Koyama, M. Yamada, T. Goto, Y. Makihara, H. Fujii, K. Watanabe .  Magnetic properties of Ce(Fe1-xCox)2 under high pressure .  J. Alloys Comp. 408-412   144 - 146   2006Magnetic properties of Ce(Fe1-xCox)2 under high pressureReviewed

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  • K. Hachitani, H. Amanuma, H. Fukazawa, Y. Kohori, K. Koyama, KI, Kumagai, C. Sekine, I. Shirotani .  Appearance of successive phase transition in SmRu4P12 under high magnetic fields probed by 31P nuclear magnetic resonance .  J. Phsy. Soc. Jpn75   124712   2006Appearance of successive phase transition in SmRu4P12 under high magnetic fields probed by 31P nuclear magnetic resonanceReviewed

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  • Y. Adachi, K. Izaki, T. Kitai, H. Yoshida, K. Koyama, H. Morita, H. Onodera, T. Kawae and T. Kaneko .  Field-induced transitions in single crystals of TbCu4Ag and GdCu4Ag .  J. Phys.: Conf. Ser.51   55 - 58   2006Field-induced transitions in single crystals of TbCu4Ag and GdCu4AgReviewed

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  • T. Hori, K. Koyama, H. Shiraishi and K. Watanabe .  Magnetic properties of NdxEr1-xMn6Sn6 alloys .  J. Phys.: Conf. Ser.51   47 - 50   2006Magnetic properties of NdxEr1-xMn6Sn6 alloysReviewed

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  • T. Hori, H. Shiraishi, K. Ohoyama, M. Nishi, K. Koyama and K. Watanabe .  Magnetic structure of Y1-xNdxMn6Sn6 alloys .  Physica B385-386   320 - 322   2006Magnetic structure of Y1-xNdxMn6Sn6 alloysReviewed

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  • H. Nishihara, T. Kanomata, Y. Furutani, T. Igarashi, K. Koyama and T. Goto .  NMR properties of half-Heusler CoVSb .  Phys. Stat. Sol. (c)3   2779 - 2782   2006NMR properties of half-Heusler CoVSbReviewed

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  • D.X. Li, T. Yamamura, S. Nimori, K. Koyama and Y. Shiokawa .  Magnetic properties of rare-earth compounds GdPdIn and TmPdIn .  J. Alloys. Comp.418   151 - 154   2006Magnetic properties of rare-earth compounds GdPdIn and TmPdInReviewed

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  • T. Kanomata, T. Igarashi, H. Nishihara, K. Koyama, K. Watanabe, K.U. Neumann, K.R.Z. Ziebeck .  Magnetic properties of weak itinerant electron ferromagnet CoVSb .  Mater. Trans.47   496 - 500   2006Magnetic properties of weak itinerant electron ferromagnet CoVSbReviewed

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  • J. Prchal, H. Kitazawa, T. Furubayashi, P. Javorsky and K. Koyama .  Low-temperature structural study of the TbPd1-xNix series .  Physica B378-380   1102 - 1104   2006Low-temperature structural study of the TbPd1-xNix seriesReviewed

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  • D.X. Li, S. Nimori, Y.X. Li, K. Koyama and Y. Shiokawa .  Magnetic ordering in ternary germanide Nd2CuGe6 .  J. Alloys. Comp.408-412   122 - 126   2006Magnetic ordering in ternary germanide Nd2CuGe6Reviewed

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  • K. Koyama, S. Miura, H. Okada, T. Shigeoka, S. Fujieda, A. Fujita, K. Fukamichi and K. Watanabe, .  Magnetocaloric and structural properties of SmMn2Ge2 .  J. Alloys. Comp. 408-412   118 - 121   2006Magnetocaloric and structural properties of SmMn2Ge2Reviewed

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  • H. Okada, K. Koyama, and K. Watanabe .  Specific heat measurement of the spinel compound CuV2S .  the AIP Conference Proceedings850   1317 - 1318   2006Specific heat measurement of the spinel compound CuV2SReviewed

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  • A. Himori, S. Ohishi, K. Koyama, K. Watanabe, and T. Shigeoka .  Mulitstep metamagnetism of NdRh2Ge2 single crystal .  J. Phys.: Conf. Ser.51   63 - 66   2006Mulitstep metamagnetism of NdRh2Ge2 single crystalReviewed

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  • E.A. Tereshina, H. Yoshida, A.V. Andreev, I.S. Tereshina, K. Koyama, and T. Kanomata .  Interplay between hydrogenation and pressure effects in magnetism of Lu2Fe17 single crystal .  High Pressure Res.26   485 - 488   2006Interplay between hydrogenation and pressure effects in magnetism of Lu2Fe17 single crystalReviewed

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  • A.V. Andreev, K. Koyama, N.M. Mushnikov, V. Sechovsky, Y. Shiokawa, I. Satoh, and K. Watanabe .  Interplay between effects of external pressure and dilution of the U sublattice in UCoAl-base materials: the U0.94Y0.06CoAl case .  High Pressure Res.26   475 - 478   2006Interplay between effects of external pressure and dilution of the U sublattice in UCoAl-base materials: the U0.94Y0.06CoAl caseReviewed

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  • K. Koyama, F. Ishikawa, and K. Watanabe .  High field x-ray diffraction studies on magnetic refrigerants .  Int. J Appl. Electromagnetics and Mechanics23   153 - 163   2006High field x-ray diffraction studies on magnetic refrigerantsReviewed

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  • K. Watanabe, G. Nishijima, S. Awaji, K. Koyama, K. Takahashi, N. Kobayashi and T. Kiyoshi .  Cryocooled superconducting magnets for high magnetic fields at the HFLSM and future collaboration with the TML .  J. Phys.: Conf. Ser.51   631 - 634   2006Cryocooled superconducting magnets for high magnetic fields at the HFLSM and future collaboration with the TMLReviewed

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  • K. Koyama, S. Miura, H. Okada, and K. Watanabe .  Development of an extraction type magnetometer under high pressure and high magnetic fields over 200 kOe in the hybrid magnet .  J. Phys.: Conf. Ser.51   569 - 572   2006Development of an extraction type magnetometer under high pressure and high magnetic fields over 200 kOe in the hybrid magnetReviewed

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  • K. Takahashi, S. Awaji, Y. Sasaki, K. Koyama and K. Watanabe .  Design of an 8 MW water-cooled magnet for a 35 T hybrid magnet at the HFLSM .  IEEE Trans. Appl. Supercond.16   977 - 980   2006Design of an 8 MW water-cooled magnet for a 35 T hybrid magnet at the HFLSMReviewed

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  • T. Ito, M. Ishizuka, T. Tsurudome, H. Ookubo, J. Sakuraba, S. Awaji, G. Nishijima, K. Koyama, K. Takahashi and K. Watanabe .  Development of a 10 T cryocooled superconducting magnet with a room temperature bore of 360 mm for a 29 T hybrid magnet .  Adv. Cryo. Eng.51   1743 - 1748   2006Development of a 10 T cryocooled superconducting magnet with a room temperature bore of 360 mm for a 29 T hybrid magnetReviewed

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  • 高橋弘紀、淡路智、佐々木嘉信、小山佳一、渡辺和雄 .  小型冷凍機冷却34T-8MWハイブリッドマグネットへの発展と磁気科学応用 .  低温工学41   316 - 321   2006小型冷凍機冷却34T-8MWハイブリッドマグネットへの発展と磁気科学応用Reviewed

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  • K. Watanabe, G. Nishijima, S. Awaji, K. Takahashi, K. Koyama, N. Kobayashi, M. Ishizuka, T. Itou, T. Tsurudome and J. Sakuraba .  Performance of a cryogen-free 30 T-class hybrid magnet .  IEEE trans. Appl. Superc.16   934 - 939   2006Performance of a cryogen-free 30 T-class hybrid magnetReviewed

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  • 秋屋貴博、加藤宏明、佐川眞人、小山佳一、宮崎照宣 .  Nd-Dy-Fe-B系焼結磁石の強磁場中熱処理と保磁力 .  J. Magn. Soc. Jpn.30   447 - 454   2006Nd-Dy-Fe-B系焼結磁石の強磁場中熱処理と保磁力Reviewed

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  • H. Kato, H. Kubota, K. Koyama and T. Miyazaki .  Fabrication of SmFe12/α-Fe thin films as anisotropic nanocomposite magnet .  J. Alloys. Comp.408-412   1368 - 1372   2006Fabrication of SmFe12/α-Fe thin films as anisotropic nanocomposite magnetReviewed

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  • V. Provenzano, B. Baumgold, R.D. Shull, A.J. Shapiro, K. Koyama, K. Watanabe, N.K. Singh, K.G. Suresh, A.K. Nigam, S.K. Malik .  Structure and magnetocaloric properties of the Fe-doped HoTiGe alloy .  J. Appl. Phys.99   08K906   2006Structure and magnetocaloric properties of the Fe-doped HoTiGe alloyReviewed

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  • F. Ishikawa, K. Koyama, K. Watanabe, T. Asano, and H. Wada .  First-order phase transition at the Curie temperature in MnAs and MnAs0.9Sb0.1 .  J. Phys. Soc. Jpn75   84604   2006First-order phase transition at the Curie temperature in MnAs and MnAs0.9Sb0.1Reviewed

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  • H. Yabuta, K. Umeo, T. Takabatake, K. Koyama and K. Watanabe .  Temperature- and field-induced first-order ferromagnetic transitions in MnFe(P1-xGex) .  J. Phys. Soc. Jpn75   113707   2006Temperature- and field-induced first-order ferromagnetic transitions in MnFe(P1-xGex)Reviewed

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  • K. Koyama, H. Okada, K. Watanabe, T. Kanomata, R. Kainuma, W. Ito, K. Oikawa, K. Ishida .  Observation of large magnetoresistance of magnetic Heusler alloy Ni50Mn36Sn14 in high magnetic fields .  Appl. Phys. Lett.89   182510   2006Observation of large magnetoresistance of magnetic Heusler alloy Ni50Mn36Sn14 in high magnetic fieldsReviewed

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  • K. Koyama, T. Kanomata, R. Kainuma, K. Oikawa, K. Ishida and K. Watanabe, .  High field X-ray diffraction measurements of novel ferromagnetic shape-memory alloy Ni50Mn36Sn14 .  Physica B383   24 - 26   2006High field X-ray diffraction measurements of novel ferromagnetic shape-memory alloy Ni50Mn36Sn14Reviewed

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  • K. Koyama, K. Watanabe, T. Kanomata, R. Kainuma, K. Oikawa, and K. Ishida .  Observation of field-induced reverse transformation in ferromagnetic shape memory alloy Ni50Mn36Sn14 .  Appl. Phys. Lett.88   132505   2006Observation of field-induced reverse transformation in ferromagnetic shape memory alloy Ni50Mn36Sn14Reviewed

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  • V.A. Chernenko, V.A. Lvov, T. Kanomata, T. Kakeshita, K. Koyama and S. Besseghini .  Martensitic transformation in Ni-Mn-Ga alloy under high magnetic fields .  Mater. Trans.47   635 - 638   2006Martensitic transformation in Ni-Mn-Ga alloy under high magnetic fieldsReviewed

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  • K. Koyama, T. Kanomata, T. Watanabe, T. Suzuki, H. Nishihara, and K. Watanabe .  X-ray powder diffraction studies of Mn3Ga0.97Al0.03C in magnetic fields .  Mater. Trans. 47   492 - 495   2006X-ray powder diffraction studies of Mn3Ga0.97Al0.03C in magnetic fieldsReviewed

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  • K. Yagasaki, S. Notsu, Y. Takaesu, T. Nakama, E. Sakai, K. Koyama, K. Watanabe and A.T. Burkov .  X ray diffraction on rare earth-3d Laves phase compound of ErCo2 in magnetic field .  Physica B378-380   1089 - 1090   2006X ray diffraction on rare earth-3d Laves phase compound of ErCo2 in magnetic fieldReviewed

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  • S.V. Demishev, A.V. Semeno, A.A. Pronin, N.E. Sluchanko, N.A. Samarin, H. Ohta, S. Okubo, M. Kimata, K. Koyama, M. Motokawa and A.V. Kuznetsov .  Low-temperature study of the quantum critical phenomena in CuGeO3:Fe .  J. Magn. Magn. Matter.300   e346 - e349   2006Low-temperature study of the quantum critical phenomena in CuGeO3:FeReviewed

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  • M. Kimata, H. Ohta, K. Koyama, M. Motokawa, R. Kondo, S. Kagoshima, H. Tanaka, M. Tokumoto, H. Kobayashi, and A. Kobayashi .  Fermi surface study of organic conductors using a magneto-optical measurement under high magnetic fields .  J. Phys.: Conf. Ser.51   359 - 362   2006Fermi surface study of organic conductors using a magneto-optical measurement under high magnetic fieldsReviewed

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  • M. Kimata, Y. Oshima, K. Koyama, H. Ohta, M. Motokawa, H. Nishikawa, K. Kikuchi, I. Ikemoto .  Detailed fermi surface topology of the quasi-one-dimensional conductor (DMET)2I3 .  J. Low Temp. Phys.142   523 - 526   2006Detailed fermi surface topology of the quasi-one-dimensional conductor (DMET)2I3Reviewed

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  • H. Kato, T. Akiya, M. Sagawa, K. Koyama, T. Miyazaki .  Field-induced alignment of Nd-rich phase and coercivity in sintered Nd-Fe-B magnets .  INTERMAG 2006 - IEEE International Magnetics Conference   914   2006

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    DOI: 10.1109/INTMAG.2006.374945

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  • A. Himori, S. Ohishi, K. Koyama, K. Watanabe, T. Shigeoka .  Multistep metamagnetism of NdRh2Ge2 single crystal .  YAMADA CONFERENCE LX ON RESEARCH IN HIGH MAGNETIC FIELDS51   63 - +   2006

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    Measurements of high-field magnetization up to 18 T, magnetic susceptibility and specific heat have been performed on a tetragonal NdRh2Ge2 single crystal and polycrystalline sample. From the temperature dependences of magnetic susceptibilities, this compound shows an antiferromagnetic behaviour with Neel temperature of 50 K. Another magnetic transition is observed at 37 K. At low temperatures, a multi-step metamagnetic behaviour is observed along the easy c-axis and a strong magnetic anisotropy is seen. The saturation magnetic moment is estimated to be 2.76 mu(B)/f.u.. There are five magnetic phases below the induced ferromagnetic phase in the H-T magnetic phase diagram. To discuss the magnetic behaviours, the CEF analysis has been made.

    DOI: 10.1088/1/1742-6596/51/1/012

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  • T. Hori, K. Koyama, H. Shiraishi, K. Watanabe .  Magnetic properties of Nd(x)Erl(1-x)Mn(6)Sn(6) alloys .  YAMADA CONFERENCE LX ON RESEARCH IN HIGH MAGNETIC FIELDS51   47 - +   2006

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    We have conducted low- and high-field magnetization measurements and neutron diffraction experiments on NdxEr1-xMn6Sn6 alloys (0 &lt;= x &lt;= 0.5) with hexagonal MgFe6Ge6 type structure. The alloy with x = 0.1 shows a complex helical antiferromagnetism with the magnetic moments rotating in the c plane below the Curie temperature T-C = 340 K, and a ferrimagnetism below the temperature T-t = 100 K. In the ferrimagnetic state, the magnetic moments mu(Mn) and mu(Nd) are parallel to each other, and antiparallel to mu(Er). The alloy with x = 0.4 shows also a similar ferrimagnetic structure below the Curie temperature T-C = 360 K. It is likely that the each magnetic moments are keep a constant values of mu(Mn) = 2.3 mu(B)/Mn atom, mu(Nd) = 3 mu(B)/Nd atom and mu(Er) = 9 mu(B)/Nd atom at 10 K in the whole composition (0 &lt; x &lt;= 0.5). The ferrimagnetic arrangements for the alloys with 0.2 &lt;= x &lt;= 0.5 are not almost disturbed by magnetic field up to 26 T at 4.2 K.

    DOI: 10.1088/1/1742-6596/51/1/008

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  • A. V. Andreev, E. Santava, Y. Homma, K. Koyama, T. Yamamura, Y. Shiokawa .  Magnetic anisotropy of U2Co17-xSix single crystals. .  Recent Advances in Actinide Science, May, I.; Alvares, R.; Bryan, N., Eds. The Royal Society of Chemistry: Cambridge   758 - 760   2006Magnetic anisotropy of U2Co17-xSix single crystals.Reviewed

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  • A. V. Andreev, K. Koyama, N. V. Mushnikov, V. Sechovsky, Y. Shiokawa, I. Satoh, K. Watanabe .  Interplay between effects of external pressure and dilution of the U-sublattice in UCoAl-based materials: the U0.94Y0.06CoAl case .  High Pressure Research26 ( 4 ) 475 - 478   2006

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    Substitution of Y for U in the itinerant 5f-electron metamagnet, UCoAl, transforms the system to a ferromagnetic state. Application of external hydrostatic pressure above 0.3GPa suppresses the spontaneous ferromagnetism and restores the paramagnetism with field-induced transition to ferromagnetic state. However, the transition becomes of the second order instead of the first-order one in parent UCoAl. © 2006 Taylor &amp
    Francis.

    DOI: 10.1080/08957950601103973

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  • Hironari Okada, Keiichi Koyama, Kazuo Watanabe .  Specific heat measurement of the spinel compound CuV2S4 .  LOW TEMPERATURE PHYSICS, PTS A AND B850   1317 - +   2006Specific heat measurement of the spinel compound CuV2S4Reviewed

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    We have performed specific heat measurements of a high-quality polycrystalline sample of CuV2S4. Two anomalies associated with charge density wave (CDW) transitions are clearly observed at T-t1 = 92 K and T-t2h = 58 K. The anomalies at T-t1 and T-t2h show lambda-type and spike-shaped behavior, indicating second and first order phase transitions, respectively. The electronic specific heat coefficient gamma and the Debye temperature Theta(D) are estimated to be 36 mJ/moIK(2) and 347 K, respectively. gamma of CuV2S4 is much larger than that of CuTi2S4, whereas CuTi2S4 exhibits a CDW gap at low temperature. This enhancement of gamma is probably attributed not only to the electron-phonon interaction but also to electron-electron interactions.

    DOI: 10.1063/1.2355192

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  • H. Kato, K. Koyama, T. Miyazaki .  Effect of high-magnetic-field annealing on the magnetic properties of Nd-Co-B nanocomposite ribbons .  INTERMAG ASIA 2005: Digests of the IEEE International Magnetics Conference   167   2005.12

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  • M Kimata, Y Oshima, K Koyama, H Ohta, M Motokawa, HM Yamamoto, R Kato .  Fermi surface study of beta ''-(BEDT-TTF)(TCNQ) by magnetooptical measurements .  SYNTHETIC METALS153 ( 1-3 ) 369 - 372   2005.9

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    We have performed magnetooptical measurements of beta ''-(BEDT-TTF)(TCNQ) using a cavity perturbation technique with a millimeter vector network analyzer (MVNA) and a 14 T superconducting magnet at IMR, Tohoku University. The results of ADMRO and SdH measurements at low temperatures are not consistent with the band calculation result. Therefore, we are interested in Fermi surfaces at low temperatures and have performed magnetooptical measurements of beta ''-(BEDT-TTF)(TCNQ). Although the band calculation and ADMRO results suggest the existence of Q1D FS, our results suggest the existence of Q2D FS only. From the results of magnetooptical measurements, we discuss the FS topology of this system at low temperatures.

    DOI: 10.1016/j.synthmet.2005.07.308

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  • JL Her, K Koyama, K Watanabe, Provenzano, V, AQ Fu, AJ Shapiro, RD Shull .  High-magnetic field X-ray diffraction studies on Gd-5(Ge2-xFex)Si-2 (x=0.05 and 0.2) .  MATERIALS TRANSACTIONS46 ( 9 ) 2011 - 2014   2005.9

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    We performed the powder X-ray diffraction measurements in magnetic fields up to 5T for Gd-5(Ge1.95Fe0.05)Si-2 and Gd-5(Ge(1.8)Fc(0.2))Si-2-With heating from 8 K, the matrix of Gd-5(Ge1.95Fe0.05)Si-2 clearly shows a structural transition from an orthorhombic to a monoclinic structure at the Curie temperature (Tc = 276 K). On the other hand, the matrix of Gd-5(Ge1.8Fe0.2)Si-2 with the orthorhombic structure in the ferromagnetic state shows two-phases co-existence of the orthorhombic and the monoclinic structures above Tc = 303 K, indicating that a small amount of the matrix participates in the transformation. For both samples, the monoclinic structure is suppressed but the orthorhombic structure is enhanced just above Tc by applying a magnetic field, which closely relates to the magnetization process.

    DOI: 10.2320/matertrans.46.2011

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  • M Kimata, K Koyama, H Ohta, Y Oshima, M Motokawa, H Nishikawa, K Kikuchi, Ikemoto, I .  Development and applications of magnetooptical measurement system equipped with a rotational resonant cavity in the millimeter-wave region .  JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS44 ( 7A ) 4930 - 4934   2005.7

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    A rotational resonant cavity equipped with a millimeter vector network analyzer (MVNA) and a 14T solenoid type superconducting magnet has been developed. The available frequency range is about 50-100GHz. The temperature can decrease to 1.5 K. The cavity can rotate within the precision of one degree. As an example of the application of the new resonant cavity, we have performed detailed magnetooptical measurements of an organic conductor to estimate the Fermi surface topology. The Fermi surface of the quasi-one-dimensional conductor (DMET)(2)I(3) is discussed.

    DOI: 10.1143/JJAP.44.4930

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  • H Kato, M Ishizone, K Koyama, T Miyazaki .  Realization of anisotropic nanocomposite magnet in Nd2Fe14B/alpha-Fe thin films .  JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS290   1221 - 1225   2005.4

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    A series of Nd2Fe14B/&alpha;-Fe nanocomposite thin films, in which the crystallites of the Nd2Fe14B phase are well-oriented, has been synthesized by RF magnetron sputtering onto heated glass substrates. Magnetization curves exhibited single-phase-like hysteresis loops, suggesting that the two phases are firmly exchange-coupled. By comparing the observed magnetization curves with the micromagnetic calculations, we have estimated the intergrain exchange-coupling constants. &COPY; 2004 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jmmm.2004.11.407

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  • S Miura, K Koyama, H Okada, T Shigeoka, K Watanabe .  High-field X-ray diffraction measurement of SmMn2Ge2 .  JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS44 ( 3 ) 1258 - 1259   2005.3

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    The high-field X-ray diffraction measurement of a re-entrant ferromagnet SmMn2Ge2 with a tetragonal structure was carried out. The unit cell volume contracts by approximately 0.3% in the antiferromagnetic (AFM) state, compared with that of the ferromagnetic (FM) state. In the AFM state, the structural distortion recovers due to a high magnetic field, accompanied by the metamagnetic transition from the AFM state to the forced FM state.

    DOI: 10.1143/JJAP.44.1258

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  • S. Okubo, D. Fukuoka, M. Kimata, H. Ohta, Y. Inagaki, T. Kumimoto, K. Koyama, M. Motokawa, Z. Hiroi .  Oshikawa-Affleck electron spin resonance behavior observed in one-dimensional antiferromagnet BaCu2(Si1-xGex)2O7 (x=0.65) .  J. Phys. Soc. Jpn, Suppl.74   80 - 85   2005.1Oshikawa-Affleck electron spin resonance behavior observed in one-dimensional antiferromagnet BaCu2(Si1-xGex)2O7 (x=0.65)Reviewed

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  • H. Okada, K. Koyama and K. Watanabe .  Transport, magnetic, thermal and structural properties of the spinel compound CuTi2S4 .  J. Alloys Comp.403   34 - 37   2005Transport, magnetic, thermal and structural properties of the spinel compound CuTi2S4Reviewed

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  • T. Tsutaoka, Y. Nakamori, K. Koyama and T. Tokunaga .  Magnetic and electrical properties of Gd7Rh3 single crystal .  J. Magn. Magn. Mater.293   768 - 773   2005Magnetic and electrical properties of Gd7Rh3 single crystalReviewed

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  • K. Koyama, T. Kanomata and K. Watanabe .  High field X-ray diffraction studies on MnFeP0.5As0.5 .  Jpn. J. Appl. Phys., 44   L549 - L551   2005High field X-ray diffraction studies on MnFeP0.5As0.5Reviewed

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  • H. Kato, M. Ishizone, K. Koyama and T. Miyazaki .  Realization of anisotropic nanocomposite magnet in Nd2Fe14B/a-Fe thin films .  J. Magn. Magn. Mater.290-291   1221 - 1225   2005Realization of anisotropic nanocomposite magnet in Nd2Fe14B/a-Fe thin filmsReviewed

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  • J.L. Her, K. Koyama, K. Watanabe, V. Provenzano, A. Fu, A.J. Shapiro, and R.D. Shull .  High field X-ray diffraction studies on Gd5(Ge2-xFex)Si2 (x=0.05 and 0.2) .  Mater. Trans.46   2011 - 2014   2005High field X-ray diffraction studies on Gd5(Ge2-xFex)Si2 (x=0.05 and 0.2)Reviewed

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  • K. Koyama, T. Kanomata, T. Matsukawa and K. Watanabe .  Magnetic field effect on structural property of MnFeP0.5As0.5 .  Mater. Trans.46   1753 - 1756   2005Magnetic field effect on structural property of MnFeP0.5As0.5Reviewed

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  • T. Kanomata, T. Nozawa, D. Kikuchi, H. Nishihara, K. Koyama and K. Watanabe .  Magnetic properties of ferromagnetic shape memory alloys Ni2-xCuxMnGa .  Int. J Appl. Electromagnetics and Mechanics21   151 - 157   2005Magnetic properties of ferromagnetic shape memory alloys Ni2-xCuxMnGaReviewed

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  • S. Miura, K. Koyama, H. Okada, T. Shigeoka and K. Watanabe, .  High-field X-ray diffraction measurements of SmMn2Ge2 .  Jpn. J. Appl. Phys.44   1258 - 1259   2005High-field X-ray diffraction measurements of SmMn2Ge2Reviewed

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  • M. Yoshida, K. Koyama, A. Ochiai, and M. Motokawa .  Cyclotron resonance in rare-earth monopnictides .  Phys. Rev. B71   75102   2005Cyclotron resonance in rare-earth monopnictidesReviewed

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  • H. Ohta, M. Kimata, K. Koyama, Y. Oshima, M. Motokawa, H. Nishikawa, K. Kikuchi, I. Ikemoto .  Magneto-optical measurement of organic conductor using rotational cavity system .  Int. J. Infrared and Millimeter Wave26   1525 - 1530   2005Magneto-optical measurement of organic conductor using rotational cavity systemReviewed

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  • T. Sakon, K. Koyama, M. Motokawa, A. Muller, B. Barbara, Y. Ajiro .  Detailed ESR measurements for the quantum molecular magnet V15 at ultra-low temperatures .  Prog. Theor. Phys. suppl.159   302 - 307   2005Detailed ESR measurements for the quantum molecular magnet V15 at ultra-low temperaturesReviewed

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  • S.V. Demishev, A. Semeno, A. Proin, N. Sluchanko, N. Samarin, H. Ohta, S. Okubo, M. Kimata, K. Koyama, M. Motokawa, .  The competition between staggered field and antiferromagnetic interaction in CuGeO3:Fe .  Prog. Theor. Phys. suppl.159   387 - 391   2005The competition between staggered field and antiferromagnetic interaction in CuGeO3:FeReviewed

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  • M. Kimata, Y. Oshima, K. Koyama, H. Ohta, M. Motokawa, H.M. Yamamoto, R. Kato .  Fermi surface study of β”-(BEDT-TTF)(TCNQ) by magnetooptical measurements .  Synthetic Metals153   369 - 372   2005Fermi surface study of β”-(BEDT-TTF)(TCNQ) by magnetooptical measurementsReviewed

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

  • S.V. Demishev, A.V. Semeno, N.E. Sluchanko, N.A. Samarin, A.A. Pronin, V.V. Glushkov, H. Otha, S. Okubo, M. Kimata, K. Koyama, M. Motokawa, A.V. Kuznetsov .  Disorder-driven quantum critical behaviour in CuGeO3 doped with magnetic impurity .  Physica B359-361   1315 - 1317   2005Disorder-driven quantum critical behaviour in CuGeO3 doped with magnetic impurityReviewed

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  • M. Kimata, K. Koyama, H. Ohta, Y. Oshima, M. Motokawa, H. Nishikawa, K. Kikuchi and I. Ikemoto .  The development and the applications of the magnetooptical measurement system equipped with a rotational resonant cavity in the millimeter-wave region .  Jpn. J. Appl. Phys.44   4930 - 4934   2005The development and the applications of the magnetooptical measurement system equipped with a rotational resonant cavity in the millimeter-wave regionReviewed

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  • KIMATA M, OHTA H, KOYAMA K, OSHIMA Y, MOTOKAWA M, YAMAMOTO H, KATO R .  Development of the High Field Magneto-optical Measurement System with a Rotational Cavity .  in High magnetic Fields in Semiconductor Physics, Yong-Jie Wang, Lloyd Engel and N. Bonesteel Eds.World Scientific, Singapore 35   2005Development of the High Field Magneto-optical Measurement System with a Rotational CavityReviewed

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  • KIMATA Motoi, OHTA Hitoshi, KOYAMA Keiichi, OSHIMA Y, MOTOKAWA Mitsuhiro, YAMAMOTO M H, KATO R .  Development of the High Field Magneto-optical Measurement System with a Rotational Cavity for the Study of Organic Conductors, in High magnetic Fields in Semiconductor Physics, Yong-Jie Wang, Lloyd Engel and N. Bonesteel Eds. .  World Scientific, Singapore, 2005pp355-358.   2005Development of the High Field Magneto-optical Measurement System with a Rotational Cavity for the Study of Organic Conductors, in High magnetic Fields in Semiconductor Physics, Yong-Jie Wang, Lloyd Engel and N. Bonesteel Eds.

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  • Susumu Okubo, Daisuke Fukuoka, Motoi Kimata, Hitoshi Ohta, Yuji Inagaki, Takashi Kumimoto, Keiichi Koyama, Mitsuhiro Motokawa, Zenji Hiroi .  Oshikawa-Affleck Electron Spin Resonance Behavior Observed in One-Dimensional Antiferromagnet BaCu2(Si1-xGex)(2)O-7 (x=0.65) .  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN74   2005Oshikawa-Affleck Electron Spin Resonance Behavior Observed in One-Dimensional Antiferromagnet BaCu2(Si1-xGex)(2)O-7 (x=0.65)Reviewed

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    Submillimeter and millimeter wave electron spin resonance (ESR) measurements of BaCu2(Si1-xGex)(2)O-7, which is a mixed system of an S=1/2 one-dimensional Heisenberg antiferromagnet with the Dzyaloshinskii-Moriya interaction, have been performed to investigate the limitations of the Oshikawa-Affleck theory for the ESR of an S=1/2 one-dimensional Heisenberg antiferromagnet with a staggered field. The magnetic field dependence of the linewidth and the field induced energy gap will be discussed in connection with the Oshikawa-Affleck theory.

    DOI: 10.1143/JPSJ.74.80

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  • S Demishev, A Semeno, A Pronin, N Sluchanko, N Samarin, H Ohta, S Okubo, M Kimata, K Koyama, M Motokawa .  The competition between staggered field and antiferromagnetic interactions in CuGeO3 : Fe .  PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT159 ( 159 ) 387 - 391   2005

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    The EPR spectra along different crystallographic axes for single crystals of CuGeO3 containing 1% of Fe impurity have been studied in the frequency range 60-360 GHz at temperatures 0.5-30 K. The analysis based on the Oshikawa-Affleck theory suggests that the temperature dependences of the line width and g-factor are formed as a result of the competition between interchain antiferromagnetic interactions and staggered Zeeman energy. It is found that staggered magnetic moments in CuGeO3:Fe are located predominantly along b axis.

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  • K Irisawa, A Fujita, K Fukamichi, M Yamada, H Mitamura, T Goto, K Koyama .  Transition between antiferromagnetic and ferromagnetic states in itinerant-electron La(FexAl1-x)(13) compounds .  PHYSICAL REVIEW B70 ( 21 ) 1 - 16   2004.12

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    The transition between the antiferromagnetic (AF) and the ferromagnetic (F) states has been investigated with regard to the magnetovolume effect and the spin-fluctuation characteristics in La(FexAl1-x)(13) compounds. The volume V and amplitude of the local magnetic moment M-loc are different between the AF and F states. In the AF state, the field-induced first-order AF-F transition appears and the transition proceeds with two steps in higher Fe concentration regions. The complex temperature dependence of the AF-F transition field is explained by the contribution from both the magnetic and elastic energies caused by the significant temperature variation of amplitude of M-loc. For the two-step transitions, the spin-floplike transition and the increase in amplitude of M-loc occur at the first- and second-step transitions, respectively. In other words, both the localized moment and the itinerant-electron characteristics are concurrently observed.

    DOI: 10.1103/PhysRevB.70.214405

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  • M Kimata, H Ohta, K Koyama, Y Oshima, M Motokawa, HM Yamamoto, R Kato .  Development of the high field magneto-optical measurement system with a rotational cavity for the study of organic conductors .  INTERNATIONAL JOURNAL OF MODERN PHYSICS B18 ( 27-29 ) 3803 - 3806   2004.11

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    We have developed a new magneto-optical measurement system with a rotational cavity. It consists of a millimeter vector network analyzer and a 15T solenoid type superconducting magnet and it can go down to 1.5 K. The rotational cavity can be used in the transmission configuration and the rotation can be performed up to almost 360 degrees in 1 degree precision. We will show the magneto-optical measurement results of, beta ''-(BEDT-TTF)(TCNQ) using our new system. We observe the quasi-two-dimensional periodic orbit resonance (POR) in beta ''-(BEDT-TTF)(TCNQ). The Fermi surfaces of this system will be discussed.

    DOI: 10.1142/S0217979204027487

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  • H Okada, K Koyama, S Miura, M Yamada, T Goto, Y Makihara, H Fujii, K Watanabe .  Pressure effect on the magnetic properties of Ce(Fe1-xCox)(2) .  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN73 ( 7 ) 1982 - 1986   2004.7

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    We have studied the magnetic properties of Ce(Fe1-xCox)(2) with x less than or equal to 0.1 by magnetization measurements under high pressures up to 1.2 GPa. In pure CeFe2, the Curie temperature T-C decreases, and the saturation magnetization M-s is suppressed by applying pressure. In Co substitution compounds, the transition temperature T-A from the ferromagnetic (FM) to the antiferromagnetic (AFM) states and the metamagnetic transition field B-c increase with increasing pressure, while T-C and the magnetization of the spontaneous and field-induced FM states decrease. The obtained results indicate that the AFM state becomes stable by the lattice contraction.

    DOI: 10.1143/JPSJ.73.1982

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  • T Hasebe, S Okada, M Ishizuka, T Tsurudome, T Ito, H Ookubo, J Sakuraba, K Watanabe, S Awaji, K Koyama, G Nishijima, K Takahashi .  Design of a cryocooler-cooled large bore superconducting magnet for a 30 T hybrid magnet .  IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY14 ( 2 ) 368 - 371   2004.6

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

    We are now developing a 30 T hybrid magnet utilizing a cryocooler-cooled superconducting magnet wound with highly strengthened (Nb, Ti)(3)Sn. Diameter of the room temperature bore of the superconducting magnet is 360 mm and it generates 11.1 T. Water cooled resistive insert magnet generates 18.9 T, thus the hybrid magnet generates a central field of 30.0 T. The (Nb, Ti)(3)Sn multifilamentary wires are strengthened by Cu/NbTi composite which volume ratio in conductor is about 35%. The reinforcing Cu/NbTi composite changes to CuTi intermetallic compounds during heat treatment for reaction of (Nb, Ti)(3)Sn phase formation. The Nb3Sn coil with inner diameter of 400 mm will be fabricated by wind and react method with Cu/NbTi reinforced (Nb, Ti)(3)Sn wires. The innermost section of Nb3Sn coil is wound with a wire which diameter is 1.85 mm and next second section is wound with a wire diameter of 1.8 mm. The Nb3Sn coil is operated at 303 A and generates 5.8 T. The NbTi coil is wound with NbTi wires of 2.0 mm and 1.6 mm diameters. The NbTi coil generates 5.3 T at an operating current of 350 A. The maximum hoop stress is under 220 MPa for Nb3Sn coil and 200 MPa for NbTi coil.

    DOI: 10.1109/TASC.2004.829672

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  • A Fujita, K Fukamichi, K Koyama, K Watanabe .  X-ray diffraction study in high magnetic fields of magnetovolume effect in itinerant-electron metamagnetic La(Fe0.88Si0.12)(13) compound .  JOURNAL OF APPLIED PHYSICS95 ( 11 ) 6687 - 6689   2004.6

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    Magnetovolume effect due to the itinerant-electron metamagnetic (IEM) transition in La(Fe0.88Si0.12)(13) has been investigated by x-ray diffraction measurements in high magnetic fields. No crystal structure change was confirmed after the IEM transition. The relative change in the lattice constant measured perpendicular to the magnetic field direction is similar to the longitudinal linear magnetostriction, and hence the volume change due to the IEM transition is isotropic. The volume change in both the ferromagnetic and the paramagnetic states is proportional to the square of the magnetization, though the magnetovolume coupling constant in the former is smaller than that in the latter. (C) 2004 American Institute of Physics.

    DOI: 10.1063/1.1667455

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  • B Ohta, S Okubo, D Fukuoka, Y Inagaki, T Kunimoto, M Kimata, K Koyama, M Motokawa, Z Hiroi .  Breather excitation observed by high-field ESR in one-dimensional antiferromagnet BaCu2(Si1-xGex)(2)O-7 (x=0.65) .  JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS272   929 - 930   2004.5

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    We have performed the high-field ESR of the one-dimensional BaCu2(Si1-xGex)(2)O-7 (x = 0.65) antiferromagnet at 0.5 and 1.8 Kin the wider frequency and magnetic field region (40-500 GHz, up to 30 T), and found the breather excitation predicted by the Oshikawa-Affleck (OA) theory. The observed field-induced gap for Bparallel toc (chain direction) shows the B-2/3 dependence suggested by the OA theory, and the dependence is weak for the other directions which is consistent with the anisotropy of the Dzyaloshinsky-Moriya interaction. The results will be also discussed in connection with the breather excitation observed in Cu-benzoate. (C) 2003 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jmmm.2003.12.547

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  • Keiichi Koyama, Takeshi Kanomata, Tatsuo Watanabe, Takanori Suzuki, Hironori Nishihara, Kazuo Watanabe .  Magnetic transitions in Mn3Ga1-xAlxC (0 &lt;= x &lt;= 0.1) .  JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS272   E615 - E617   2004.5Magnetic transitions in Mn3Ga1-xAlxC (0 &lt;= x &lt;= 0.1)Reviewed

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    We have performed the magnetization and X-ray diffraction measurements on Mn3Ga1-xAlxC (0 &lt;= x &lt;= 0.1) with a perovskite-type structure in the temperature T range from 5 to 400 K to investigate the behavior of the complicated magnetic phase transitions. The obtained results suggest that the crystallographic character is closely correlated to the magnetic properties. The new magnetic phase diagram of this system is presented, which indicates the two-phases coexistence in Mn3Ga1-xAlxC at lower temperature. (C) 2003 Elsevier B. V. All rights reserved.

    DOI: 10.1016/j.jmmm.2003.11.312

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  • M Itoi, A Taira, M Enomoto, N Matsushita, N Kojima, Y Kobayashi, K Asai, K Koyama, T Nakano, Y Uwatoko, J Yamaura .  Crystal structure and structural transition caused by charge-transfer phase transition for iron mixed-valence complex (n-C3H7)(4)N[(FeFeIII)-Fe-II(dto)(3)] (dto = C2O2S2) .  SOLID STATE COMMUNICATIONS130 ( 6 ) 415 - 420   2004.5

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    (n-C3H7)(4)N[(FeFeIII)-Fe-II(dto)(3)] shows a new type of first order phase transition called chare-transfer phase transition around 120 K. where the charge transfer between Fe-II and Fe-III occurs reversibly. Recently, we have succeeded in obtaining single crystals of the title complex and determined the crystal Structure at room temperature. Crystal data: space group P6(3), a = 10.0618(5) Angstrom. c = 16.0424(7) Angstrom. V = 1406.54(12)Angstrom, Z = 2. Moreover. we have investigated the structural transition caused by the charge-transfer phase transition by means of powder X-ray diffraction measurement. When the temperature is decreased. the a-axis. which corresponds to the hexagonal ring size in two-dimensional honeycomb network structure of [Fe-II Fe-III(dto)(3)](infinity). contracts by 0.1 Angstrom at the charge-transfer transition temperature (T-CT) while the c-axis. perpendicular to the honeycomb network layer. elongates by 0.1 Angstrom at T-CT. Consequently, when the temperature is decreased, the unit cell volume decreases without noticeable anomaly around T-CT, which is responsible for the quite sniall vibrational contribution to the entropy change. compared with usual spin crossover transition. Thus, the charge-transfer phase transition around 120 K for (n-C3H7)(4)N[Fe-II Fe-III(dto)(3)] is regarded as spin entropy driven phase transition. (C) 2004 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.ssc.2004.02.034

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  • Y Makihara, K Koyama, K Fukushima, K Watanabe, H Fujii .  X-ray diffraction study on Ce(Fe1-xCox)(2) in high field at low temperature .  JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS272   608 - 610   2004.5

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    The temperature and magnetic field dependences of lattice parameter for Ce(Fe1-xCox)(2) with x = 0, 0.05 and 0.10 are examined by powder X-ray diffraction measurement. The strong correlation between structural phase and magnetic state in these compounds is discussed. (C) 2003 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jmmm.2003.11.245

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  • K Koyama, K Fukushima, M Yamada, T Goto, Y Makhara, H Fujii, K Watanabe .  High-field X-ray diffraction and high-pressure magnetization measurements of the pseudobinary compound Ce(Fe0.9Co0.1)(2) .  PHYSICA B-CONDENSED MATTER346   187 - 190   2004.4

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    The magnetic and structural properties of Ce(Fe0.9Co0.1)(2) with the C15 cubic Laves-phase structure have been studied by magnetization measurement in high magnetic fields under high pressures, and powder X-ray diffraction measurement in fields up to 5 T. The C15 cubic structure is distorted to rhombohedral symmetry accompanied with the magnetic phase transition from the ferromagnetic to the antiferromagnetic state, which recovered the C15 structure by applying the magnetic field. The antiferromagnetic phase is induced by the lattice contraction due to hydrostatic pressure. Obtained results suggest that the AFM correlation due to the Cc 4f-Fe 3d hybridization plays an important role on the structural and magnetic properties. (C) 2004 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physb.2004.01.047

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  • Y Oshima, M Kimata, K Kishigi, H Ohta, K Koyama, M Motokawa, H Nishikawa, K Kikuchi, Ikemoto, I .  Observation of high-order quasi-one-dimensional periodic orbit resonance in (DMET)(2)I-3 and its Fermi surface .  PHYSICA B-CONDENSED MATTER346   387 - 391   2004.4

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    Magneto-optical measurements of a quasi-one-dimensional (q1D) organic superconductor (DMET)(2)I-3 has been performed by using a cavity perturbation technique. Several resonant absorption lines, which can be attributed to the q1D periodic orbit resonance (q1D POR), as well as the quite unusual high-order q1D POR coming from the corrugated Fermi surface (FS) in the interlayer direction were observed. Moreover, other harmonic resonances are also observed when the AC electric field is applied along the c*-axis. We will also show its estimated q1D FS from the data analysis where the estimated FS clearly shows why there is no spin-density-wave or charge-density-wave transition in (DMET)(2)I-3 despite having a q1D FS. (C) 2004 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physb.2004.01.112

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  • M Kimata, Y Oshima, H Otha, K Koyama, M Motokawa, HM Yamamoto, R Kato .  Magnetooptical measurements of beta ''-(BEDT-TTF)(TCNQ) .  PHYSICA B-CONDENSED MATTER346   382 - 386   2004.4

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    Magnetooptical measurements have been performed on beta"-(BEDT-TTF)(TCNQ) using the cavity perturbation techniques. beta"-(BEDT-TTF)(TCNQ) has very exotic Fermi surface (FS). Several harmonic resonances were observed at various angles. We consider these resonances as q1D-periodic orbit resonance. The obtained Fermi velocity and the scattering time are 4.4 x 10(4) m/s and 2.1 x 10(-11) s, respectively. When the magnetic field was rotated in the b*a-plane, the similar resonances are observed. According to these results, the FS topology of the system at low temperature is discussed. (C) 2004 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physb.2004.01.111

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  • K Koyama, K Fukushima, Y Makihara, H Fujii, K Watanabe .  X-ray diffraction study on the pseudobinary compound Ce(Fe0.9Co0.1)(2) in high magnetic fields .  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN73 ( 3 ) 676 - 680   2004.3

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    We have studied the magnetic and structural properties of Ce(Fe0.9Co0.1)(2) with the C15 cubic Laves-phase structure by low-temperature x-ray diffraction measurements in magnetic fields up to 5 T, and in the temperature range from 9 to 300 K. The C15 structure is distorted to rhombohedral symmetry at 90 K in zero magnetic field, accompanied with the magnetic phase transition from the ferromagnetic (FM) to the antiferromagnetic (AFM) states with decreasing temperature. In the AFM state, it is observed clearly that the rhombohedral distortion state recovers the C15 structure by applying magnetic field, accompanied with the metamagnetic transition from the AFM to the forced FM states with a hysteresis in the magnetization process.

    DOI: 10.1143/JPSJ.73.676

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  • H. Okada, K. Koyama, S. Miura, M. Yamada, T. Goto, Y. Makihara, H. Fujii, K. Watanabe, .  Pressure effect on the magnetic properties of Ce(Fe1-xCox)2 .  J. Phys. Soc. Jpn.73   1982 - 1986   2004Pressure effect on the magnetic properties of Ce(Fe1-xCox)2Reviewed

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  • O. Nashima, T. Kanomata, Y. Yamaguchi, S. Abe, T. Harada, T. Suzuki, H. Nishihara, K. Koyama, T. Shishido, K. Watanabe and T. Kaneko .  Magnetic and electrical properties of Fe3-xVxSi .  J. Alloys and Compounds383   298 - 301   2004Magnetic and electrical properties of Fe3-xVxSiReviewed

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  • H. Wada, H. Yoshida, T. Goto and K. Koyama .  Field-induced magnetic transitions of exchange competing system GdMn2Ge2 .  J. Magn. Magn. Matter.272-276   591 - 592   2004Field-induced magnetic transitions of exchange competing system GdMn2Ge2Reviewed

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  • K. Koyama, T. Kanomata, T. Watanabe, T. Suzuki, H. Nishihara, and K. Watanabe .  Magnetic transitions in Mn3Ga1-xAlxC (0<x<0.1) .  J. Magn. Magn. Matter.272-276   e615 - e617   2004Magnetic transitions in Mn3Ga1-xAlxC (0<x<0.1)Reviewed

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  • T. Fujiwara, Y. Uwatoko, H. Fujii, K. Koyama, M. Motokawa, and T. Shigeoka .  The correlation between the phase transition and valence change of the Yb ionic state induced upon pressurization in YbMn2Ge2 .  J. Magn. Magn. Matter.272-276   599 - 600   2004The correlation between the phase transition and valence change of the Yb ionic state induced upon pressurization in YbMn2Ge2Reviewed

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  • X. Fan, T. Mashimo, X. Huang, T. Kagayama, A. Chiba, K. Koyama and M. Motokawa .  Magnetic properties of Co-Cu metastable solid solution alloys .  Phys. Rev. B69   94432   2004Magnetic properties of Co-Cu metastable solid solution alloysReviewed

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  • H. Okada, K. Koyama and K. Watanabe .  Two-step structural modulations and Fermi liquid state in spinel compound CuV2S4 .  J. Phys. Soc. Jpn.73   3227 - 3230   2004Two-step structural modulations and Fermi liquid state in spinel compound CuV2S4Reviewed

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  • A. Fujita, K. Fukamichi, K. Koyama, and K. Watanabe .  X-ray diffraction study in high magnetic fields of magnetovolume effect in itinerant-electron metamagnetic La(Fe0.88Si0.12)13 compound .  J. Appl. Phys.95   6687 - 6689   2004X-ray diffraction study in high magnetic fields of magnetovolume effect in itinerant-electron metamagnetic La(Fe0.88Si0.12)13 compoundReviewed

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  • M. Kimata, Y. Oshima, H. Ohta, K. Koyama, M. Motokawa, H.M. Yamamoto, and R. Kato .  Magnetooptical measurement of β’’-(BEDT-TTF)(TCNQ) .  Physica B346-347   382 - 386   2004Magnetooptical measurement of β’’-(BEDT-TTF)(TCNQ)Reviewed

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

  • K. Kobayashi, T. Akiya, H. Kato and K. Koyama .  Relation between a specific lattice expansion and magnetic anisotropy in Sm2Fe17Nx (0<x<3) samples of intermediate nitrogen concentration .  proceedings for 18th workshop on high performance magnets & their applications, (Annecy, 2004)   521 - 528   2004Relation between a specific lattice expansion and magnetic anisotropy in Sm2Fe17Nx (0<x<3) samples of intermediate nitrogen concentrationReviewed

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  • K. Watanabe, G. Nishijima, S. Awaji, K. Takahashi, K. Koyama, M. Motokawa, M. Ishizuka, T. Hasebe, and J. Sakuraba .  Advances in the first cryogen-free hybrid magnet .  IEEE Trans. Appl. Superc. 14   388 - 392   2004Advances in the first cryogen-free hybrid magnetReviewed

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  • T. Hasebe, S. Okada, M. Ishizuka, T. Tsurudone. T. Ito, H. Ookubo, J. Sakuraba, K. Watanabe, S. Awaji, K. Koyama, G. Nishijima, and K. Takahashi .  Design of a cryocooler-cryocooled large bore superconducting magnet for a 30T hybrid magnet .  IEEE Trans. Appl. Superc.14   368 - 371   2004Design of a cryocooler-cryocooled large bore superconducting magnet for a 30T hybrid magnetReviewed

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  • T. Kurusu, M. Ono, S. Hanai, M. Kyoto, H. Takigami, H. Takano, K. Watanabe, S. Awaji, K. Koyama, G. Nishijima, K. Togano .  A cryocooler-cooled 19 T superconducting magnet with 52 mm room temperature bore .  IEEE Trans. Appl. Superc.14   393 - 396   2004A cryocooler-cooled 19 T superconducting magnet with 52 mm room temperature boreReviewed

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  • K. Watanabe, S. Awaji, G. Nishijima, K. Takahashi, K. Koyama, M. Motokawa, and N. Kobayashi .  Magnet technology and materials research at the High-Field Laboratory for Superconducting Materials .  Physica B346-347   618 - 622   2004Magnet technology and materials research at the High-Field Laboratory for Superconducting MaterialsReviewed

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  • K. Takahashi, C. Umeki, I. Mogi, K. Koyama, S. Awaji, M. Motokawa, and K. Watababe .  Magnetic orientation of paraffin in a magnetic levitation furnace .  Physica B346-347   277 - 281   2004Magnetic orientation of paraffin in a magnetic levitation furnaceReviewed

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  • H. Kato, T. Miyazaki, M. Sagawa and K. Koyama .  Coercivity enhancements by high-magnetic-field annealing in sintered Nd-Fe-B magnets .  Appl. Phys. Lett.84   4230 - 4232   2004Coercivity enhancements by high-magnetic-field annealing in sintered Nd-Fe-B magnetsReviewed

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  • K. Irisawa, A. Fujita, K. Fukamichi, M. Yamada, H. Mitamura, T. Goto and K. Koyama .  Transition between antiferromagnetic and ferromagnetic states in itinerant-electron La(FexAl1-x)13 compounds .  Phys. Rev. B70   214405   2004Transition between antiferromagnetic and ferromagnetic states in itinerant-electron La(FexAl1-x)13 compoundsReviewed

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  • K. Koyama, M. Sakai, T. Kanomata and K. Watanabe .  Field-induced martensitic transformation in new ferromagnetic shape memory compound Mn1.07Co0.92Ge .  Jpn. J. Appl. Phys.43   8036 - 8039   2004Field-induced martensitic transformation in new ferromagnetic shape memory compound Mn1.07Co0.92Ge Reviewed

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  • D. Kikuchi, T. Kanomata, Y. Yamaguchi, H. Nishihara, K. Koyama, and K. Watanabe .  Magnetic properties of ferromagnetic shape memory alloys Ni2Mn1-xFexGa .  J. Alloys and Compounds383   184 - 188   2004Magnetic properties of ferromagnetic shape memory alloys Ni2Mn1-xFexGaReviewed

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  • Y. Makihara, K. Koyama, K. Fukushima, K. Watanabe, and H. Fujii .  X-ray diffraction study on Ce(Fe1-xCox)2 in high field at low temperature .  J. Magn. Magn. Matter.272-276   608 - 610   2004X-ray diffraction study on Ce(Fe1-xCox)2 in high field at low temperatureReviewed

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  • K. Koyama, K. Fukushima, Y. Makihara, H. Fujii, and K. Watanabe .  X-ray diffraction study on the psudobinary compound Ce(Fe0.9Co0.1)2 in high magnetic fields .  J. Phys. Soc. Jpn.73   676 - 680   2004X-ray diffraction study on the psudobinary compound Ce(Fe0.9Co0.1)2 in high magnetic fieldsReviewed

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  • F. Ishikawa, K. Koyama, K. Watanabe, and H. Wada, .  X-ray diffraction study of the structural phase transition in MnAs under high magnetic fields .  Physica B346-347   408 - 412   2004X-ray diffraction study of the structural phase transition in MnAs under high magnetic fieldsReviewed

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  • K. Koyama, K. Fukushima, M. Yamada, T. Goto, Y. Makihara, H. Fujii, and K. Watanabe .  High field x-ray diffraction and high pressure magnetization measurements of the pseudobinary compound Ce(Fe0.9Co0.1)2 .  Physica B346-347   187 - 190   2004High field x-ray diffraction and high pressure magnetization measurements of the pseudobinary compound Ce(Fe0.9Co0.1)2Reviewed

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  • F. Ishikawa, K. Koyama, K. Watanabe, T. Asano, and H. Wada .  Structural transformation of MnAs1-xSbx under high magnetic fields .  Mater. Trans.45   311 - 314   2004Structural transformation of MnAs1-xSbx under high magnetic fieldsReviewed

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  • Y. Oshima, M. Kimata, K. Kishigi, H. Ohta, K. Koyama, M. Motokawa, H. Nishikawa, K. Kikuchi, and I. Ikemoto .  Observation of high-order quasi-one-dimensional periodic orbit resonance in (DMET)2I3 and its Fermi surface .  Physica B346-347   387 - 391   2004Observation of high-order quasi-one-dimensional periodic orbit resonance in (DMET)2I3 and its Fermi surfaceReviewed

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  • M. Kimata, H. Ohta, K. Koyama, Y. Oshima, M. Motokawa, H.M. Yamamoto, R. Kato .  Development of high field magneto-optical measurement system with a rotational cavity for the study of organic conductors .  Int. J. Mod. Phys.18   3803 - 3806   2004Development of high field magneto-optical measurement system with a rotational cavity for the study of organic conductorsReviewed

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  • M. Yoshida, K. Koyama, M. Shirakawa, A. Ochiai, K. Watanabe, and M. Motokawa .  Cyclotron resonance measurements of the high-quality single crystal GdSb .  J. Magn. Magn. Matter.272-276   495 - 496   2004Cyclotron resonance measurements of the high-quality single crystal GdSbReviewed

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  • H. Ohta, O. Okubo, K. Fukuoka, Y. Inagaki, T. Kunimoto, M. Kimata, K. Koyama, M. Motokawa and Z. Hiroi .  Breather excitation observed by high-field ESR in one-dimensional antiferromagnet BaCu2(Si1-xGex)2O7 (x = 0.65) .  J. Magn. Magn. Matter272-276   929 - 930   2004Breather excitation observed by high-field ESR in one-dimensional antiferromagnet BaCu2(Si1-xGex)2O7 (x = 0.65)Reviewed

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  • K. Koyama, T. Tomimatsu, M. Yoshida, D.X. Li, and M. Motokawa .  ESR measurements of GdBi .  Physica B346-347   155 - 159   2004ESR measurements of GdBiReviewed

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  • T. Sakon, K. Koyama, M. Motokawa, Y. Ajiro, and B. Barbara, "ESR experiments of molecular magnet V15 at ultra-low temperatures .  ESR experiments of molecular magnet V15 at ultra-low temperatures .  Physica B346-347   206 - 210   2004ESR experiments of molecular magnet V15 at ultra-low temperaturesReviewed

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  • Fumihiro Ishikawa, Keiichi Koyama, Kazuo Watanabe, Tetsuya Asano, Hirofumi Wada .  Structural Transformation of MnAs1-xSbx under High Magnetic Fields .  Materials Transactions45 ( 2 ) 311 - 314   2004Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Japan Institute of Metals (JIM)  

    Structural transformation induced by magnetic fields on MnAs and MnAs 0.9Sb0.1 was investigated by the X-ray diffraction measurements in high magnetic fields up to 5T. The X-ray diffraction profiles at 319 K for MnAs showed a single phase of the orthorhombic MnP-type structure in zero field, and applying a magnetic field of 3 T caused an appearance of the hexagonal NiAs-type structure. On further increase of magnetic fields, the single phase with the hexagonal structure was confirmed above 3.5 T in a forced ferromagnetic state. The X-ray diffraction profiles at 295 K for MnAs 0.9Sb0.1 showed the hexagonal NiAs-type structure. However, the coexistence of two kinds of the NiAs-type structure with different lattice parameters was confirmed in the magnetic field of 2.5 T. The two phase coexistence was also confirmed in the temperature variation measurements in zero magnetic field. The lattice volume of the ferromagnetic phase was 1.1% larger than that of the paramagnetic phase. These results imply that the transition at TC for MnAs0.9Sb0.1 is of the first-order.

    DOI: 10.2320/matertrans.45.311

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  • H Ohta, M Kimata, K Koyama, Y Oshima, M Motokava, H Nishikawa, K Kikuchi, Ikemoto, I .  Millimeter wave magneto-optical measurement of organic conductors using a rotational cavity .  CONFERENCE DIGEST OF THE 2004 JOINT 29TH INTERNATIONAL CONFERENCE ON INFRARED AND MILLIMETER WAVES AND 12TH INTERNATIONAL CONFERENCE ON TERAHERTZ ELECTRONICS   379 - 380   2004

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    We have developed a rotational resonant cavity equipped with the millimetre vector network analyser and the 14 T superconducting solenoid magnet. The measurement can be performed down to 1.6 K and the frequency range is about 50100 GHz. As an example of its application, the results of the precise angular dependence measurements of the quasi one dimensional organic conductor (DMET)(2)I-3 are presented.

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  • M Yoshida, K Koyama, M Motokawa .  Cyclotron resonance experiments on rare-earth monopnictides .  JOURNAL OF PHYSICS-CONDENSED MATTER15 ( 28 ) S2119 - S2122   2003.7

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    Cyclotron resonance (CR) measurements on high-quality single crystals of rare-earth monopnictides have been performed in the frequency range from 50 to 190 GHz. We have successfully observed CR signals for a strongly correlated electron system, CeSb, as well as other rare-earth monopnictides, LaSb and PrSb. We have also observed Doppler-shifted CR including nonlinear behaviour in the frequency-field diagrams.

    DOI: 10.1088/0953-8984/15/28/333

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  • Keiichi Koyama, Makoto Yoshida, Dexin Li, Mitsuhiro Motokawa .  Electron Spin Resonance of GdX (X=P, As, Sb and Bi) .  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN72   2003.6Electron Spin Resonance of GdX (X=P, As, Sb and Bi)Reviewed

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    Electron spin resonance (ESR) measurements on single crystals of GdX (X = P, As, Sb and Bi) have been performed in the temperature range from 50 to 1.7 K and in the frequency range from 50 to 109 GHz to obtain microscopic information on the magnetic properties. The results obtained indicate that GdX is an "easy-plane" antiferromagnet with the magnetic moment lying in the (111) plane below the Neel temperature. In addition, ESR affected by hyperfine interaction was observed in GdBi.

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  • T Sakon, K Koyama, M Motokawa, H Nojiri, T Asano, Y Ajiro .  Electron spin resonance measurements at ultralow temperatures .  PHYSICA B-CONDENSED MATTER329   1629 - 1631   2003.5

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    An electron spin resonance (ESR) measurement system for use at ultralow temperatures using a He-3-He-4 dilution refrigerator has been developed down to 160 mK. As the first experiment, the ESR was measured on a quantum spin chain Cu benzoate, in which a field-induced gap was recently found. The evaluation of a new ESR mode, so-called breather mode, was found at the lowest temperatures. In the present work, we observed a smaller gap in Hparallel tob by suppressing of the thermal excitation. (C) 2003 Elsevier Science B.V. All rights reserved.

    DOI: 10.1016/S0921-4526(02)02433-X

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  • T Suzuki, H Matsui, H Tsuchiya, E Negishi, K Koyama, N Toyota .  Antiferromagnetic resonance in lambda-(BEDT-TSF)(2)FeCl4 .  SYNTHETIC METALS135 ( 1-3 ) 567 - 568   2003.4

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    An antiferromagnetic resonance in lambda-(BETS)(2)FeCl4 has been observed at 23-110 GHz in the antiferromagnetic insulating state. The frequency-field diagram, which is basically explained by a two-sublattice model, indicates that the spin system has a biaxial anisotropy and the a(*)-axis is close to the hard axis.

    DOI: 10.1016/S0379-6779(02)00745-2

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  • Y Oshima, H Ohta, K Koyama, M Motokawa, H Nishikawa, K Kikuchi, Ikemoto, I .  Magnetooptical measurements of quasi-one-dimensional conductor (DMET)(2)I-3 .  SYNTHETIC METALS135 ( 1-3 ) 531 - 532   2003.4

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    Magnetooptical measurements of quasi-one-dimensional organic conductor (DMET)(2)I-3 have been performed by using a cavity perturbation technique with Millimeter Vector Network Analyzer (MVNA). Several resonances are observed and these resonances disappear when the magnetic field is applied nearby the conducting b-axis. These resonances seem to come from the periodic modulation of group velocities of the carriers on the quasi-one-dimensional Fermi surface (q1D FS). However, these resonances show a different angular dependence with the Fermi traversal resonance (FTR) or quasi-one-dimensional periodic orbit resonance (q1D POR).

    DOI: 10.1016/S0379-6779(02)00721-X

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  • H Ohta, Y Oshima, Y Inagaki, S Okubo, M Kimata, M Motokawa, T Mori .  Magneto-optical measurements of beta-(BEDT-TTF)(2)AuI2 .  SYNTHETIC METALS135 ( 1-3 ) 527 - 528   2003.4

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    Magneto-optical measurements of beta-(BEDT-TTF)(2)Aul(2), which has an isotropic two dimensional Fermi surface in the ab-plane, have been performed at 1.8 K by using cavity perturbation technique with steady magnetic field and mosaic transmission technique with pulsed magnetic field. A cyclotron resonance coming from the quasi two dimensional Fermi surface has been observed in both measurements for Hperpendicular toab-plane. Obtained effective mass was 0.9 m, and this result is smaller than the mass obtained by the Shubnikov-de Haas measurement, which suggests the existence of electron-electron interactions in the system.

    DOI: 10.1016/S0379-6779(02)00718-X

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  • Tsutomu Mashimo, Xinsheng Huang, Xu Fan, Keiichi Koyama, Mitsuhiro Motokawa .  Erratum: Slater-Pauling curve of Fe-Cu solid solution alloys (Physical Review B - Condensed Matter and Materials Physics (2002) 66 (132407)) .  Physical Review B - Condensed Matter and Materials Physics67   999021   2003.3

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  • K Koyama, H Sasaki, T Kanomata, K Watanabe, M Motokawa .  Magnetization measurements of weak itinerant electron ferromagnet Ni-Pt alloy .  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN72 ( 3 ) 767 - 768   2003.3

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    DOI: 10.1143/JPSJ.72.767

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  • T Suzuki, H Matsui, H Tsuchiya, E Negishi, K Koyama, N Toyota .  Antiferromagnetic resonance in lambda-(BEDT-TSF)(2)FeCl4 .  PHYSICAL REVIEW B67 ( 2 )   2003.1Antiferromagnetic resonance in lambda-(BEDT-TSF)(2)FeCl4Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMERICAN PHYSICAL SOC  

    From microwave cavity transmission measurements at 23-110 GHz on lambda-(BEDT-TSF)(2)FeCl4, we have observed an antiferromagnetic resonance (AFMR) in the antiferromagnetic insulating state below the metal-to-insulator transition temperature of T-MI=8.3 K. The frequency-field dependence is fundamentally reproduced with a two-sublattice model for a biaxial anisotropy. The easy axis is confirmed to be the direction tilted by 30degrees from c to b(*), and the hard axis is found to be close to a(*). The spin-flop field is identified to be 1.3 T through the frequency-field dependence for the easy axis. The AFMR is interpreted to be caused by spin waves excited on the pi spins, exclusively due to the large pi-pi exchange interaction estimated by theoretical calculations. The exchange field and anisotropy fields for pi spin systems at 1.2 K are evaluated to be H(E)similar to330 T, H(A)(1)similar to1.5x10(-3) T for the intermediate axis and H(A)(2)similar to5.0x10(-3) T for the hard axis, respectively.

    DOI: 10.1103/PhysRevB.67.020408

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  • K. Koyama, H. Sasaki, T. Kanomata, K. Watanabe and M. Motokawa .  Magnetic properties of weak itinerant ferromagnet Ni-Pt alloy .  Physica B319-333   1121 - 1122   2003Magnetic properties of weak itinerant ferromagnet Ni-Pt alloyReviewed

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  • H. Wada, H. Yoshida, T. Goto, K. Koyama and K. Watanabe .  Novel field-induced magnetic transitions of GdMn2Ge2 .  J. Phys. Soc. Jpn72   3197 - 3203   2003Novel field-induced magnetic transitions of GdMn2Ge2Reviewed

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  • K. Koyama, H. Sasaki, T. Kanomata, K. Watanabe and M. Motokawa .  Magnetization measurements of weak itinerant ferromagnet Ni-Pt alloy .  J. Phys. Soc. Jpn72   767 - 768   2003Magnetization measurements of weak itinerant ferromagnet Ni-Pt alloyReviewed

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  • 高橋弘紀、梅木千巧、茂木巌、淡路智、小山佳一、本河光博、渡辺和雄 .  磁気浮上状態で溶融凝固したパラフィンの配向効果 .  日本応用磁気学会誌27   1125 - 1129   2003磁気浮上状態で溶融凝固したパラフィンの配向効果Reviewed

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  • F. Ishikawa, K. Koyama, K. Watanabe, and H. Wada .  Field induced structural transformation in MnAs .  Jpn. J. Appl. Phys.42   L918 - L920   2003Field induced structural transformation in MnAsReviewed

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  • T. Tomimatsu, K. Koyama, M. Yoshida, D.X. Li and M. Motokawa .  Observation of antiferromagnetic resonance affected by hyperfine interaction in GdBi .  Phys. Rev. B67   14406   2003Observation of antiferromagnetic resonance affected by hyperfine interaction in GdBiReviewed

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  • K. Koyama, M. Yoshida, D.X. Li and M. Motokawa .  Electron spin resonance of GdX (X=P, As, Sb and Bi) .  J. Phys. Soc. Jpn. Suppl. B.72   145 - 150   2003Electron spin resonance of GdX (X=P, As, Sb and Bi)Reviewed

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  • T. Sakon, H. Nojiri, K. Koyama, T. Asano, Y. Ajiro and M. Motokawa .  ESR measurements at ultra-low temperatures using a dilution refrigerator .  J. Phys. Soc. Jpn. Suppl. B72   140 - 144   2003ESR measurements at ultra-low temperatures using a dilution refrigeratorReviewed

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  • H. Ohta, Y. Oshima, Y. Inagaki, S. Okubo, M.Kimata, K. Koyama, M. Motokawa and T. Mori .  Magneto-optical measurements of β-(BEDT-TTF)2AuI2 .  Synthetic Metals135-136   527 - 528   2003Magneto-optical measurements of β-(BEDT-TTF)2AuI2Reviewed

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

  • Y. Oshima, M. Kimata, K. Kishigi. H. Ohta, K. Koyama, M. Motokawa, H. Nishikawa, K. Kikuchi and I. Ikemoto .  Fermi surface study of quasi-one-dimensional metals using magneto-optical techniques .  Phys. Rev. B68   54526   2003Fermi surface study of quasi-one-dimensional metals using magneto-optical techniquesReviewed

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  • T. Suzuki, H. Matsui, H. Tsuchiya, E. Negishi, K. Koyama, and N. Toyota .  Antiferromagnetic resonance in λ-(BEDT-TSF)2FeCl4 .  Synthetic Metals135-136   567 - 568   2003Antiferromagnetic resonance in λ-(BEDT-TSF)2FeCl4Reviewed

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

  • M. Yoshida, K. Koyama and M. Motokawa .  Cyclotron resonance experiments in rare-earth monopnictides .  J. Phys.: Condenced Matter15   S2119 - S2122   2003Cyclotron resonance experiments in rare-earth monopnictidesReviewed

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  • T. Sakon, K. Koyama, M. Motokawa, H. Nojiri, T. Asano, Y. Ajiro .  Electron spin resonance measurements at ultralow temperature .  Physica B329   1629 - 1631   2003Electron spin resonance measurements at ultralow temperatureReviewed

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  • M. Yoshida, K. Koyama, T. Tomimatsu, M. Shirakawa, A. Ochiai and M. Motokawa .  Observation of cyclotron resonance in CeSb .  Physica B329-333   557 - 558   2003Observation of cyclotron resonance in CeSbReviewed

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  • M. Yoshida, K. Koyama, T. Tomimatsu, M. Shirakawa, A. Ochiai and M. Motokawa .  Doppler-shifted cyclotron resonance with Alfven waves in LaSb .  Physica B329-333   1092 - 1093   2003Doppler-shifted cyclotron resonance with Alfven waves in LaSbReviewed

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  • M. Yoshida, K. Koyama, M. Shirakawa, A. Ochiai, K. Watanabe, and M. Motokawa .  Cyclotron resonance and magnetic resonance in GdSb .  J. Phys. Soc. Jpn.73   1763 - 1767   2003Cyclotron resonance and magnetic resonance in GdSbReviewed

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  • Y. Oshima, H. Ohta, K. Koyama, M. Motokawa, H.M. Yamamoto, R. Kato, M. Tamura, Y. Nishio and K. Kajita .  Fermi surface study of quasi-two dimensional organic conductors by magnetooptical measurements .  J. Phys. Soc. Jpn72   143 - 148   2003Fermi surface study of quasi-two dimensional organic conductors by magnetooptical measurementsReviewed

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  • Y. Oshima, H. Ohta, K. Koyama, M. Motokawa, H. Nishikawa, K. Kikuchi and I. Ikemoto .  Magnetooptical measurements of quasi-one-dimensional conductor (DMET)2I3 .  Synthetic Metals135-136   531 - 532   2003Magnetooptical measurements of quasi-one-dimensional conductor (DMET)2I3Reviewed

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  • Y. Oshima, H. Ohta, H.M. Yamamoto, R. Kato, K. Koyama, and M. Motokawa .  Magnetooptical measurements of BEDT-TTF salts containing supramolecular assemblies .  Synthetic Metals133-134   453 - 454   2003Magnetooptical measurements of BEDT-TTF salts containing supramolecular assembliesReviewed

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  • M. Yoshida, K. Koyama, P.C. Canfield, C. Cunningham, S. Nimori, K. Watanabe and M. Motokawa .  Cyclotron resonance in PrSb .  J. Phys. Soc. Jpn.72   705 - 708   2003Cyclotron resonance in PrSbReviewed

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  • T. Suzuki, H. Matsui, H. Tsuchiya, E. Negishi, K. Koyama, and N. Toyota, .  Antiferromagnetic resonance in λ-(BEDT-TSF)2FeCl4 .  Phys. Rev.B67   020408(R)   2003Antiferromagnetic resonance in λ-(BEDT-TSF)2FeCl4Reviewed

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  • N. Toyota, T. Suzuki, H. Matsui, H. Tsuchiya, E. Negishi, K. Koyama .  Antiferromagnetic resonance in (formula presented) .  Physical Review B - Condensed Matter and Materials Physics67 ( 2 )   2003

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    From microwave cavity transmission measurements at 23–110 GHz on (formula presented) we have observed an antiferromagnetic resonance (AFMR) in the antiferromagnetic insulating state below the metal-to-insulator transition temperature of (formula presented) The frequency-field dependence is fundamentally reproduced with a two-sublattice model for a biaxial anisotropy. The easy axis is confirmed to be the direction tilted by (formula presented) from c to (formula presented) and the hard axis is found to be close to (formula presented) The spin-flop field is identified to be 1.3 T through the frequency-field dependence for the easy axis. The AFMR is interpreted to be caused by spin waves excited on the (formula presented) spins, exclusively due to the large (formula presented) exchange interaction estimated by theoretical calculations. The exchange field and anisotropy fields for (formula presented) spin systems at 1.2 K are evaluated to be (formula presented) (formula presented) for the intermediate axis and (formula presented) T for the hard axis, respectively. © 2003 The American Physical Society.

    DOI: 10.1103/PhysRevB.67.020408

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  • Keiichi Koyama, Makoto Yoshida, Dexin Li, Mitsuhiro Motokawa .  Electron spin resonance of GdX (X=P, As, Sb and Bi) .  Journal of the Physical Society of Japan72   145 - 150   2003

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Physical Society of Japan  

    Electron spin resonance (ESR) measurements on single crystals of GdX (X = P, As, Sb and Bi) have been performed in the temperature range from 50 to 1.7 K and in the frequency range from 50 to 109 GHz to obtain microscopic information on the magnetic properties. The results obtained indicate that GdX is an "easy-plane" antiferromagnet with the magnetic moment lying in the (111) plane below the Néel temperature. In addition, ESR affected by hyperfine interaction was observed in GdBi. © 2003 The Physical Society Japan.

    DOI: 10.1143/JPSJS.72SB.145

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  • H Fujii, Sasaki, I, K Koyama .  Interstitial alloys as hard magnetic materials .  JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS242   59 - 65   2002.4

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    For clarifying the role that the interstitial N atoms played on the microscopic scale for basic magnetism in R2Fe17N3, we determined the enhancements of Fe magnetic moments on the crystallographically different atomic sites and crystalline electric field parameter A, upon nitrogenation by neutron diffraction studies of the rhombohedral Y2Fe17 and Y2Fe17N3.1 and high-field magnetization measurements of single crystalline Nd2Fe17 and Nd2Fe17N3, respectively. The results obtained are compared with those estimated by the band structure calculation. For clarifying the coercivity mechanism in Sm2Fe17N3, we also examined the particle (powder) size and surface cleaning effects on the coercive field mu(0)H(e) for the Sm2Fe17N3 single crystal powder. The results indicate that mu(0)H(e) monotonically decreases with increasing the particle size, suggesting that the coercivity mechanism is of a nucleation type. When there are many nucleation sites on the surface of Sm2FeN3 powder before surface cleaning, the value of mu(0)H(e) is relatively small and reveals strong temperature dependence, while mu(0)H(e) is strongly enhanced by surface cleaning, leading to relatively weak temperature dependence. (C) 2002 Elsevier Science B.V. All rights reserved.

    DOI: 10.1016/S0304-8853(01)01189-1

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  • T Sakon, K Koyama, M Motokawa .  Electron spin resonance experiments at ultralow temperatures by means of a dilution refrigerator .  REVIEW OF SCIENTIFIC INSTRUMENTS73 ( 3 ) 1242 - 1246   2002.3

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMER INST PHYSICS  

    An electron spin resonance (ESR) apparatus with a high sensitivity vector network analyzer has been developed for use at ultralow temperatures. The microwave frequency can be varied between 45 and 110 GHz. The resonant cavity was installed in a He-3-He-4 dilution refrigerator which provides ultralow temperatures down to 160 mK. In order to avoid the heating of the cavity and the sample by microwaves or heat leaks in the cryostat, attenuators and thermal anchors were placed at the most suitable positions. As the first experiment, the ESR was measured for a quantum spin chain Cu benzoate. The breather mode, which is a new ESR mode caused by a field induced gap, has been clearly observed at the lowest temperatures. (C) 2002 American Institute of Physics.

    DOI: 10.1063/1.1448901

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  • K. Koyama, T. Goto, T. Kanomata and R. Note .  Magnetization measurement of MnSi just above the critical pressure .  Physica B312-313   485 - 486   2002Magnetization measurement of MnSi just above the critical pressureReviewed

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  • T. Fujiwara, H. Fujii, K. Koyama and M. Motokawa .  Novel magnetism on single crystalline YbMn2Ge2 .  Physica B312-313   864 - 866   2002Novel magnetism on single crystalline YbMn2Ge2Reviewed

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  • Kanomata, T. Narita, N. Suzuki, K. Sato, T. Harada, N. Oogawara, K. Koyama and M. Motokawa .  Electrical properties of the transition metal compound MnRhP .  J. Alloys and Compounds334   68 - 71   2002Electrical properties of the transition metal compound MnRhPReviewed

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  • T. Mashimo, X. Huang, X. Fan, K. Koyama and M. Motokawa .  Slater-Pauling curve of Fe-Cu solid solution alloys .  Phys. Rev. B66   132407   2002Slater-Pauling curve of Fe-Cu solid solution alloysReviewed

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  • H. Fujii, I. Sasaki and K. Koyama .  Interstitial alloy as hard magnetic materials .  J. Magn. Magn. Mater. 242-245   59 - 65   2002Interstitial alloy as hard magnetic materialsReviewed

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  • T. Sakon, K. Koyama and M. Motokawa .  Electron spin resonance experiments at ultra-low temperature by means of a dilution refrigerator .  Rev. Sci. Instrum.73   1242 - 1246   2002Electron spin resonance experiments at ultra-low temperature by means of a dilution refrigeratorReviewed

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  • M. Yoshida, K. Koyama, T. Tomimatsu, M. Shirakawa, A. Ochiai and M. Motokawa .  Observation of cyclotron resonance on LaBi .  Physica B322   306 - 307   2002Observation of cyclotron resonance on LaBiReviewed

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  • M. Yoshida, K. Koyama, T. Tomimatsu, M. Shirakawa, A. Ochiai and M. Motokawa .  The observation of cyclotron resonance in LaSb .  Physica B312-313   684 - 685   2002The observation of cyclotron resonance in LaSbReviewed

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  • T. Tomimatsu, K. Koyama, M. Yoshida, D.X. Li and M. Motokawa .  Magnetic resonance of GdBi .  Physica B312-313   682 - 683   2002Magnetic resonance of GdBiReviewed

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  • K. Koyama,T. Tomimatsu, M. Yoshida, D.X. Li and M. Motokawa .  Observation of cyclotron resonance on GdSb .  Physica B312-313   680 - 681   2002Observation of cyclotron resonance on GdSbReviewed

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  • K. Koyama, M. Yoshida, T. Tomimatsu, T. Sakon, D.X.. Li, M. Shirakawa, A. Ochiai and M. Motokawa .  Observation of cyclotron resonance in rare-earth monopnictides by millimeter microwave region .  J. Phys. and Chem. of Solids.63   1227 - 1230   2002Observation of cyclotron resonance in rare-earth monopnictides by millimeter microwave regionReviewed

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  • M. Yoshida, K. Koyama, M. Shirakawa, A. Ochiai, K. Watanabe and M. Motokawa .  Cyclotron resonance in CeSb .  J. Phys. Soc. Jpn.71   2847 - 2850   2002Cyclotron resonance in CeSbReviewed

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  • Y. Oshima, H. Ohta, K. Koyama, M. Motokawa, H.M. Yamamoto and R. Kato .  Observation on high-order harmonic resonance in magnetooptical measurements of (BEDT-TTF)2Br(DIA) .  J. Phys. Soc. Jpn. 71   1031 - 1034   2002Observation on high-order harmonic resonance in magnetooptical measurements of (BEDT-TTF)2Br(DIA)Reviewed

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  • M. Yoshida, K. Koyama, T. Tomimatsu, M. Shirakawa,A. Ochiai and M. Motokawa .  Determination of cyclotron effective masses on LaSb .  J. Phys. Soc. Jpn.71   1752 - 1756   2002Determination of cyclotron effective masses on LaSbReviewed

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  • M. Yoshida, K. Koyama, M. Shirakawa, A. Ochiai, K. Watanabe and M. Motokawa .  Observation of Doppler-shifted cyclotron resonance in LaSb .  Phys. Rev. B66   233107   2002Observation of Doppler-shifted cyclotron resonance in LaSbReviewed

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  • M. Motokawa, M. Yoshida, K. Koyama .  Nonlinear cyclotron resonance of rare-earth semimetals .  Conference Digest - 27th International Conference on Infrared and Millimeter Waves, IRMMW 2002   Pl11 - Pl12   2002

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:Institute of Electrical and Electronics Engineers Inc.  

    The cyclotron resonance is the best way to determine the effective masses of conductors and it is interesting to compare them with other effective masses determined by the de Haas oscillations. According to Kohn's theorem, they are not necessarily coincident with each other because an electron-electron correlation in the strongly correlated electron systems contributes to only the case of the de Haas oscillations. This argument has been studied in the case of organic conductors. On the other hand, it has been difficult to observe the cyclotron resonance absorption in rare-earth semimetals due to necessity of high frequency equipment, high magnetic field, very low temperature and high quality specimen. We have succeeded in observing cyclotron resonance in some rare-earth monopnictide compounds RX (R=rare earth atom, X=pnictgen atom) with NaCl type crystal structure and discussed the relationship between two kinds of masses of these materials. As reference materials, nonmagnetic LaSb and PrSb were also studied. In these cases, we have found new nonlinear resonance lines in addition to the normal cyclotron resonance whose resonance frequencies are linear with respect to magnetic field intensity. We ascribe this effect to the Doppler shift caused by coupling of cyclotron motion of carriers with the Alfven wave propagating in the material.

    DOI: 10.1109/ICIMW.2002.1076051

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  • Keiichi Koyama, Makoto Yoshida, Takahiro Tomimatsu, Takuo Sakon, Dexin Li, Makoto Shirakawa, Akira Ochiai, Mitsuhiro Motokawa .  Observation of cyclotron resonance in rare-earth monopnictides microwave region .  Journal of Physics and Chemistry of Solids63 ( 6-8 ) 1227 - 1230   2002

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    The cyclotron effective masses of rare earth monopnictides were determined. These masses were obtained by cyclotron resonance (CR) measurements in the frequency range between 56 GHz and 190 GHz in the temperature range between 50 K and 0.5 K. The experimental results on CR measurements for single crystals of rare earth compounds were presented using a vector network analyzer (AB millimeter) and a resonant cavity. In addition to normal cyclotron resonance, two anomalous absorption lines were observed for the high quality single crystal of LaSb.

    DOI: 10.1016/S0022-3697(02)00053-7

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  • T Sakon, H Nojiri, K Koyama, T Asano, Y Ajiro, M Motokawa .  Electron spin resonance study of Cu benzoate using a He-3-He-4 dilution refrigerator .  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN70 ( 8 ) 2259 - 2262   2001.8

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    An electron spin resonance (ESR) measurement system for use at ultralow temperatures using a He-3-He-4 dilution refrigerator has been developed. As the first experiment. the ESR was measured on a quantum spin chain Cu benzoate clown to 160 ml. in which a field-induced gap was recently found.((4)) The evaluation of a new ESR mode. the so-called breather mode, was found at the lowest temperatures. In the previous ESR down to 0.5 K, this mode was clearly found for H // c. in which the magnitude of the gap is largest. In the present work. the achievement of low temperatures enabled us to observe a smaller gap in H // b by suppressing the thermal excitation. The magnitude of the field-induced gap evaluated from the nonlinear field dependence of the mode shows good agreement with that determined by previous specific heat measurements.

    DOI: 10.1143/JPSJ.70.2259

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  • H Kato, M Ishizone, T Miyazaki, K Koyama, H Nojiri, M Motokawa .  High-frequency ferromagnetic resonance in Nd2Fe14B/alpha-Fe nanocomposite films .  IEEE TRANSACTIONS ON MAGNETICS37 ( 4 ) 2567 - 2569   2001.7

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    Thin-film magnets, composed of nanophase dispersed Nd2Fe14B and alpha -Fe have been synthesized by rf magnetron sputtering. With increasing alpha -Fe volume fraction V-Fe the saturation magnetization increased linearly, while the coercivity decreased. Ferromagnetic resonance measurements were made by using a high-frequency and high-field ESR apparatus, which exhibited two absorption peaks. A model calculation of the resonance field was made for a simplified hard/soft two-sublattice system to analyze these results. Estimated values of the exchange-coupling constant are in good agreement with those deduced from micromagnetic analysis of the magnetization curves.

    DOI: 10.1109/20.951237

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  • Y Oshima, H Ohta, S Okubo, K Koyama, M Motokawa, M Tamura, Y Nishio, K Kajita .  Fermi surface study of theta-(BEDT-TTF)(2)I-3 by cyclotron resonance measurements .  SYNTHETIC METALS120 ( 1-3 ) 853 - 854   2001.3

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    Cyclotron resonances of quasi-two-dimensional organic conductor theta-(BEDT-TTF)(2)I-3 have been observed by using Millimeter Vector Network Analyzer (MVNA), V- and W-Band Cavity at 0.5K. Two resonances are observed, and the mode coupling in the cavity suggests that the resonances are cyclotron resonances. Obtained effective masses 1.03m(o) and 2.14m(o) are assigned to be alpha and beta orbits, respectively.

    DOI: 10.1016/S0379-6779(00)00711-6

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  • K Koyama, H Fujii, T Goto, H Fukuda, Y Janssen .  Magnetic phase transitions of Ce2Fe17 under high pressures and high magnetic fields .  PHYSICA B294   168 - 171   2001.1

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    Magnetization measurements have been performed on single-phase Ce2Fe17 with a rhombohedral structure under high pressures up to 1.2 GPa and in magnetic fields B up to 17T to clarify the pressure effect on the magnetic phase transitions. At 0.8 GPa, we observed at least seven magnetic phases in the B-T plane. The results obtained indicate that the hybridization between the Fe 3d- and Ce 4f-electron states plays an important role for the magnetic properties of Ce2Fe17. (C) 2001 Elsevier Science B.V. All rights reserved.

    DOI: 10.1016/S0921-4526(00)00634-7

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  • K. Koyama, H. Fujii, T. Goto, H. Fukuda and Y. Janssen, .  Magnetic phase transitions of Ce2Fe17 under high pressure and high magnetic fields .  Physica B294-295   168 - 171   2001Magnetic phase transitions of Ce2Fe17 under high pressure and high magnetic fieldsReviewed

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  • T. Kanomata, T. Sasaki, T. Hoshi, T. Narita, T. Harada, H. Nishihara, T. Yoshida, R. Note, K. Koyama, H. Nojiri, T. Kaneko and M. Motokawa .  Magnetic and electrical properties of Fe2+xV1-xAl .  J. Alloys and Compounds317-318   390 - 394   2001Magnetic and electrical properties of Fe2+xV1-xAlReviewed

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  • K. Koyama, T. Tomimatsu, M. Yoshida, D.X. Li and M. Motokawa .  Cyclotron resonance of GdSb .  J. Phys. Soc. Jpn.70   2371 - 2375   2001Cyclotron resonance of GdSbReviewed

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  • M. Yoshida, K. Koyama, T. Tomimatsu, M. Shirakawa, A. Ochiai and M. Motokawa .  Cyclotron resonance of LaBi .  J. Phys. Soc. Jpn.70   2078 - 2081   2001Cyclotron resonance of LaBiReviewed

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  • T. Sakon, H. Nojiri, K. Koyama, T. Asano, Y. Ajiro and M. Motokawa .  Electron spin resonance study of Cu Benzoate using 3He-4He dilution refrigerator .  J. Phys. Soc. Jpn.70   2259 - 2262   2001Electron spin resonance study of Cu Benzoate using 3He-4He dilution refrigeratorReviewed

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  • K. Koyama, M. Yoshida, D.X. Li and M. Motokawa .  Magnetic resonance of GdP .  J. Phys. Soc. Jpn.70   2774 - 2777   2001Magnetic resonance of GdPReviewed

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  • K. Koyama, M. Yoshida, T. Sakon, H. Nojiri, D.X. Li, T. Suzuki and M. Motokawa .  ESR and CR measurements of Gd monopnictides .  Physica B294-265   156 - 159   2001ESR and CR measurements of Gd monopnictidesReviewed

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  • M. Yoshida, K. Koyama, H. Hiraga, Y. Endoh and M. Motokawa .  High field ESR measurements of CoS2 .  Physica B294-295   145 - 148   2001High field ESR measurements of CoS2Reviewed

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  • Y. Oshima, H. Ohta, S. Okubo, K. Koyama, M. Motokawa, M. Tamura, Y. Nishio and K. Kajita .  High-field magnetooptical measurements of BEDT-TTF salts .  Physica B294-295   431 - 434   2001High-field magnetooptical measurements of BEDT-TTF saltsReviewed

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  • Y. Oshima, H. Ohta, S. Okubo, K. Koyama, M. Motokawa, M. Tamura, Y. Nishio and K. Kajita, .  Fermi surface study of θ-(BEDT-TTF)2I3 by cyclotron resonance measurements .  Synth. Metals. 120   853 - 854   2001Fermi surface study of θ-(BEDT-TTF)2I3 by cyclotron resonance measurementsReviewed

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  • H. Ohta, Y. Oshima, T. Sakurai, S. Okubo, T. Tanaka, K. Koyama, M. Motokawa, H. Kikuchi, H. Nagasawa, J.P. Boucher .  Observation of direct transition in S=1/2 quantum spin system Cu2(C5N12N2)2Cl4 by high field ESR .  J. Magn. Magn. Mater. 226-230   439 - 440   2001Observation of direct transition in S=1/2 quantum spin system Cu2(C5N12N2)2Cl4 by high field ESRReviewed

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  • H. Kato, M. Ishizone, T. Miyazaki, K. Koyama, H. Nojiri and M. Motokawa .  High-frequency ferromagnetic resonance in Nd2Fe14B/α-Fe nanocomposite films .  IEEE Trans. Magn.37   2567 - 2569   2001High-frequency ferromagnetic resonance in Nd2Fe14B/α-Fe nanocomposite filmsReviewed

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  • 加藤宏明、石曽根昌彦、宮崎照宣、小山佳一、野尻浩之、本河光博 .  強磁性共鳴によるナノコンポジット磁石の交換結合の評価 .  日本応用磁気学会誌25   675 - 678   2001強磁性共鳴によるナノコンポジット磁石の交換結合の評価Reviewed

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  • K. Koyama, T. Sakon, H. Nojiri and M. Motokawa .  Observation of new ESR mode at ultra low temperatures and CR of RE compounds by VNA .  proceedings for 26th IRMMW (Toulouse 2001)   1 - 6   2001Observation of new ESR mode at ultra low temperatures and CR of RE compounds by VNAReviewed

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  • Keiichi Koyama, Hironobu Fujii .  Nitrogen gas-solid reaction process and basic magnetism of the interstitially modified rare-earth transition-metal nitrides and .  Physical Review B - Condensed Matter and Materials Physics61   9475 - 9493   2000.1

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    In this paper, we present our recent results of studies of the nitrogen absorption process, magnetization measurements, and neutron powder-diffraction measurements for interstitially modified nitrides (Formula presented) Ce, Nd, and Sm) and (Formula presented) (1) The studies of nitrogen absorption rates in the (Formula presented) under various (Formula presented)-gas pressure up to 6 MPa indicated that the nitrogen absorption into grain interior is promoted by diffusion of nitrogen atoms under low (Formula presented)-gas pressure, while under high (Formula presented)-gas pressure, the nitrogen absorption is promoted by the grain growth of fully nitrogenated phase (Formula presented) rather than the diffusion, making high-pressure nitrogenation effective for synthesizing high-quality nitrides. (2) The high-field magnetization measurements of the (Formula presented) and (Formula presented) single crystals at 4.2 K indicated that interstitial modification of nitrogen atoms gives rise to a strong enhancement of crystalline electric field (CEF) acting on R atoms, leading to almost three times larger CEF-parameter (Formula presented) upon nitrogenation. (3) Neutron powder-diffraction studies of (Formula presented) and (Formula presented) with rhombohedral structure indicated that the N atoms fully occupy at the (Formula presented) site. The introduction of N atoms into (Formula presented) brought such a strong modification in the Fe magnetic moment that the moment of the (Formula presented) atoms being the nearest to the (Formula presented) atoms is the smallest, whereas the (Formula presented) and/or (Formula presented) atoms being relatively farther from the (Formula presented) atoms have the largest moments at 10 K. The results obtained are discussed on the basis of the calculated electronic band structures. © 2000 The American Physical Society.

    DOI: 10.1103/PhysRevB.61.9475

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  • K. Koyama, T. Goto, T. Kanomata and R. Note .  Observation of an itinerant metamagnetic transition in MnSi under high pressure .  Phys. Rev. B62   986 - 991   2000Observation of an itinerant metamagnetic transition in MnSi under high pressureReviewed

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  • K. Koyama and H. Fujii .  Nitrogen gas-solid process and basic magnetism of the interstitially modified rare-earth 3d transition-metal nitrides R2Fe17N3 (R=Y, Ce, Nd, Sm) and Y2Co17N3 .  Phys. Rev. B61   9475 - 9493   2000Nitrogen gas-solid process and basic magnetism of the interstitially modified rare-earth 3d transition-metal nitrides R2Fe17N3 (R=Y, Ce, Nd, Sm) and Y2Co17N3Reviewed

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  • K. Koyama, M. Yoshida, H. Nojiri, T. Sakon, M. Motokawa, D.X. Li and T. Suzuki .  Magnetic resonance of GdAs .  Physica B281-282   456 - 457   2000Magnetic resonance of GdAsReviewed

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  • K. Koyama, M. Yoshida, T. Sakon, D.X. Li, T. Suzuki and M. Motokawa .  Cyclotron resonance of GdAs .  J. Phys. Soc. Jpn69   3425 - 3428   2000Cyclotron resonance of GdAsReviewed

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  • M. Yoshida, K. Koyama, T. Sakon, A. Ochiai and M. Motokawa .  Cyclotron resonance of LaSb .  J. Phys. Soc. Jpn.69   3629 - 3632   2000Cyclotron resonance of LaSbReviewed

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  • K. Koyama, M. Yoshida, H. Nojiri, T. Sakon, D.X. Li, T. Suzuki and M. Motokawa .  Antiferromagnetic resonance and magnetic structure of GdAs .  J. Phys. Soc. Jpn.69   1521 - 1525   2000Antiferromagnetic resonance and magnetic structure of GdAsReviewed

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  • H. Kato, M. Ishizone, T. Miyazaki, K. Koyama, H. Nojiri and M. Motokawa .  Fabrication and magnetic properties of nanophase dispersed Nd2Fe14B / α-Fe and Sm2Fe17N3 / α-Fe films with crystallite orientation of hard phases .  proceedings for Sixteenth International Workshop on Rare-Earth Magnets (Sendai 2000)   547 - 549   2000Fabrication and magnetic properties of nanophase dispersed Nd2Fe14B / α-Fe and Sm2Fe17N3 / α-Fe films with crystallite orientation of hard phasesReviewed

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  • T. Sakon, H. Nojiri, K. Koyama, T. Asano, Y. Ajiro and M. Motokawa .  ESR at ultra-low temperatures and observation of new mode in Cu-Benzoate .  proceedings for EPR in the 21st century (Kobe 2000)   807 - 812   2000ESR at ultra-low temperatures and observation of new mode in Cu-BenzoateReviewed

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  • Sakon Takuo, Nakanishi Yoshiki, Yoshida Makoto, Koyama Keiichi, Takahashi Fumihiko, Nojiri Hiroyuki, Li De Xin, Suzuki Takashi, Motokawa Mitsuhiro .  dHvA Effect and Magnetic Resonance of GdAs .  JJAP Series: Physics of Strongly Correlated Electron Systems11   135 - 137   1999.12

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  • UMEO Kazunori, TAKABATAKE Toshiro, PIETRUS Thomas, LOHNEYSEN Hilbert von, OHMOTO Hirohisa, KOYAMA Keiichi, HANE Shogo, GOTO Tsuneaki .  Pressure-Induced Quantum Phase Transition in Ce_7Ni_3 .  JJAP series11   154 - 156   1999.2Pressure-Induced Quantum Phase Transition in Ce_7Ni_3

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  • H. Fujii, K. Koyama, I. Sasaki, S. Mitsudo and M. Motokawa .  Giant magnetic anisotropy in Sm2Fe17 induced by nitrogenation .  J. Magn. Soc. Jpn.23   465 - 467   1999.1Giant magnetic anisotropy in Sm2Fe17 induced by nitrogenationReviewed

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  • T. Sakon, Y. Nakanishi, M. Yoshida, K. Koyama, F. Takahashi, H. Nojiri, D. Li, T. Suzuki and M. Motokawa .  dHvA effect and magnetic resonance of GdAs .  Physics of strongly correlated electron systems, ed. T. Komatsubara, H. Fujii, Y. Onuki and H. Shiba (Japanese Journal of Applied Physics, Tokyo)   135 - 137   1999.1dHvA effect and magnetic resonance of GdAs

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  • K. Koyama, T. Goto, H. Fujii, H. Fukuda and Y. Janssen .  Magnetization measurements of Ce2Fe17 under high pressure and high magnetic fields .  J. Magn. Soc. Jpn.23   471 - 473   1999Magnetization measurements of Ce2Fe17 under high pressure and high magnetic fieldsReviewed

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  • N. Suzuki, T. Kanomata, R. Konno, T. Kaneko, H. Yamauchi, K. Koyama, H. Nojiri, Y. Yamaguchi and M. Motokawa .  Magnetic Phase diagram of CrTe1-xSbx (0.0 ?x ?1.0) .  J. Alloys and Compounds290   25 - 29   1999Magnetic Phase diagram of CrTe1-xSbx (0.0 ?x ?1.0)Reviewed

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  • K. Koyama, T. Goto, T. Kanomata and R. Note .  Precise magnetization measurements of single-crystalline FeSi under high pressure .  J. Phys. Soc. Jpn. 68   1693 - 1698   1999Precise magnetization measurements of single-crystalline FeSi under high pressureReviewed

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  • K. Koyama, H. Fujii, Y. Makihara, T. Kajitani and Morii .  Thermal expansion measurements on rhombohedral Y2Fe17 and Y2Fe17N3.1 .  J. Magn. Soc. Jpn.23   468 - 470   1999Thermal expansion measurements on rhombohedral Y2Fe17 and Y2Fe17N3.1Reviewed

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  • K. Umeo, T. Takabatake, T. Pietrus, H. B. Lohneysen, H. Ohmoto, K. Koyama, S. Hane and T. Goto .  Pressure-induced quantum phase transition in Ce7Ni3 .  Physics of strongly correlated electron systems, ed. T. Komatsubara, H. Fujii, Y. Onuki and H. Shiba (Japanese Journal of Applied Physics, Tokyo)   154 - 156   1999Pressure-induced quantum phase transition in Ce7Ni3

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  • N. Suzuki, T. Kanomata, R. Konno, T. Kaneko, H. Yamauchi, K. Koyama, H. Nojiri, Y. Yamaguchi, M. Motokawa .  Magnetic phase diagram of CrTe1-xSbx (0.0≤x≤1.0) .  Journal of Alloys and Compounds290 ( 1-2 ) 25 - 29   1999

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Elsevier BV  

    Measurements of the high field magnetization of CrTe1-xSbx (0.0≤x≤1.0) were carried out at 4.2 K in pulsed magnetic fields up to 300 kOe. The temperature dependence of the magnetization of CrTe1-xSbx was measured in the temperature range from 4.2 K to 800 K. The magnetic phase diagram of CrTe1-xSbx (0.0≤x≤1.0) was determined, which is similar to the typical one for the mixed crystals of the layered antiferromagnetic and ferromagnetic compounds proposed by de Gennes. © 1999 Elsevier Science S.A. All rights reserved.

    DOI: 10.1016/S0925-8388(99)00244-3

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  • KOYAMA K., FUJII H., MITSUDO S., MOTOKAWA M., KOUJIMA J., ANDOH Y., CANFIELD P.C. .  Magnetic Anisotropy in Single Crystals of an Interstitially Modified Nitrogen Compound, Nd_2Fe_<17>N_3 .  Journal of the Magnetics Society of Japan22 ( 4 ) 345 - 348   1998.4Reviewed

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    Language:Japanese   Publisher:The Magnetics Society of Japan  

    Single crystals of an interstitially modified nitrogen compound, Nd<sub>2</sub>Fe<sub>17</sub>N<sub>3</sub>, were successfully synthesized for the first time by means of the high-pressure N<sub>2</sub> gas nitrogenation technique. High-field magnetization curves along the rhombohedral principal axes for the Nd<sub>2</sub>Fe<sub>17</sub> and Nd<sub>2</sub>Fe<sub>17</sub>N<sub>3</sub> single crystals at 4.2 K indicated strong anisotropic behaviors, which were analyzed on the basis of a single-ion Hamiltonian including the Zeeman energy, exchange energy, and crystalline electric field (CEF) effect. The results indicate that the second-order CEF coefficient <i>A</i><sub>2</sub><sup>0</sup> reaches up to &minus;1.5 &times; 10<sup>3</sup> K/<i>a</i><sub>2</sub><sup>0</sup> at 4.2K upon nitrogenation, which is about three times as large as that for Nd<sub>2</sub>Fe<sub>17</sub>.

    DOI: 10.3379/jmsjmag.22.345

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    Other Link: http://dl.ndl.go.jp/info:ndljp/pid/10463847

  • T Kamimori, K Koyama, Y Mori, M Asano, K Kinoshita, J Mochimaru, K Konishi, H Tange .  Preferential site occupation of M atoms and the Curie temperature in Y2Fe17-xMx (M = Al, Si, Ga) .  JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS177 ( Pt.2 ) 1119 - 1120   1998.1Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:ELSEVIER SCIENCE BV  

    The Curie temperature, lattice parameters and the Fe-57 Mossbauer spectra were studied on Y2Fe17-xMx, where M = Al(0 less than or equal to x less than or equal to ), Si(0 less than or equal to x less than or equal to 3.5) and Ga(0 less than or equal to x less than or equal to 11). The analysis of Mossbauer spectrum shows the preferential site occupation of M atoms. The preference has little dependence on M. The behavior of the Curie temperature is closely related not to the lattice dimension but to the preferential site occupation of M. (C) 1998 Elsevier Science B.V. All rights reserved.

    DOI: 10.1016/S0304-8853(97)00972-4

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    Other Link: http://orcid.org/0000-0001-9117-5858

  • K. Koyama, S. Hane, K. Kamishima and T. Goto .  Instrument for high resolution magnetization measurements at high pressures, high magnetic fields and low temperatures .  Rev. Sci. Instrum.69   3009 - 3014   1998Instrument for high resolution magnetization measurements at high pressures, high magnetic fields and low temperaturesReviewed

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  • T. Kamimori, K. Koyama, Y. Mori, M Asano, K. Kinoshita, J. Mochimaru, K. Konishi and H. Tange, .  Preferential site occupation of N atoms and the Curie temperature in Y2Fe17-xMx (M=Al, Si, Ga) .  J. Magn. Magn. Mater.177-181   1119 - 1120   1998Preferential site occupation of N atoms and the Curie temperature in Y2Fe17-xMx (M=Al, Si, Ga)Reviewed

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  • K. Koyama, T. Goto, H. Fujii, N. Takeshita, N. Mori, H. Fukuda and Y. Janssen .  Observation of new magnetic phases in Ce2Fe17 under high pressure and high magnetic fields .  J. Phys. Soc. Jpn.67   1879 - 1882   1998Observation of new magnetic phases in Ce2Fe17 under high pressure and high magnetic fieldsReviewed

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  • K. Umeo, T. Takabatake, H. Ohmoto, T. Pietrus, H. B. Lohneysen, K. Koyama, S. Hane and T. Goto .  Low-temperature specific heat and magnetic susceptibility near the pressure-induced quantum phase transition in Ce7Ni3 .  Phys. Rev. B58   12095 - 12099   1998Low-temperature specific heat and magnetic susceptibility near the pressure-induced quantum phase transition in Ce7Ni3Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)  

  • 小山佳一、藤井博信、光藤誠太郎、本河光博、香嶋純、安藤由和、P.C. Canfield .  窒素侵入型化合物Nd2Fe17N3 単結晶の磁気異方性 .  日本応用磁気学会誌22   345 - 348   1998窒素侵入型化合物Nd2Fe17N3 単結晶の磁気異方性Reviewed

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

  • K. Koyama, T. Kajitani, Y. Morii, H. Fujii, M. Akayama .  Neutron powder diffraction of rhombohedral Y2Fe17 and Y2Fe17N3.1 .  Physical Review B55 ( 17 ) 11414 - 11421   1997.5Reviewed

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    Publishing type:Research paper (scientific journal)   Publisher:American Physical Society (APS)  

    DOI: 10.1103/physrevb.55.11414

    Other Link: http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.55.11414/fulltext

  • K. Koyama, T. Kajitani, Y. Morii, H. Fujii and M. Akayama .  Neutron powder diffraction of rhombohedral Y2Fe17 and Y2Fe17N3.1 .  Phys. Rev. B55   11414 - 11421   1997Neutron powder diffraction of rhombohedral Y2Fe17 and Y2Fe17N3.1Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)  

  • K. Koyama, H. Fujii, S. Mitsudo, M. Motokawa, J. Koujima, Y. Andoh and P.C. Canfield .  High-field magnetization on interstitially modified single crystals Nd2Fe17Z3 (Z=H and N) .  Physica B237-238   548 - 550   1997High-field magnetization on interstitially modified single crystals Nd2Fe17Z3 (Z=H and N)Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)  

  • H. Fujii, K. Koyama, K. Tatami, S. Mitsudo, M. Motokawa, T. Kajitani, Y. Morii and P.C. Canfield .  Recent development of basic magnetism in interstitially-modified rare earth iron nitrides R2Fe17N3 .  Recent development of basic magnetism in interstitially-modified rare earth iron nitrides R2Fe17N3237-238   534 - 540   1997Recent development of basic magnetism in interstitially-modified rare earth iron nitrides R2Fe17N3Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)  

  • K. Koyama, H. Fujii, S. Suzuki .  Magnetic properties of interstitially modified compounds Sm3(Fe,M)29Zx (M  Ti, V, Cr and Z  H or N) .  Journal of Magnetism and Magnetic Materials161   118 - 126   1996.8Magnetic properties of interstitially modified compounds Sm3(Fe,M)29Zx (M  Ti, V, Cr and Z  H or N)Reviewed

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    Publishing type:Research paper (scientific journal)   Publisher:Elsevier BV  

    DOI: 10.1016/s0304-8853(96)00054-6

  • K. Koyama, H. Fujii, P.C. Canfield .  Magnetocrystalline anisotropy of a Nd2Fe17 single crystal .  Physica B: Condensed Matter226 ( 4 ) 363 - 369   1996.8Magnetocrystalline anisotropy of a Nd2Fe17 single crystalReviewed

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    Publishing type:Research paper (scientific journal)   Publisher:Elsevier BV  

    DOI: 10.1016/0921-4526(96)00267-0

  • H. Fujii, K. Tatami, K. Koyama .  Nitrogenation process in Sm2Fe17 under various N2-gas pressures up to 6 MPa .  Journal of Alloys and Compounds236 ( 1-2 ) 156 - 164   1996.4Nitrogenation process in Sm2Fe17 under various N2-gas pressures up to 6 MPaReviewed

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    Publishing type:Research paper (scientific journal)   Publisher:Elsevier BV  

    DOI: 10.1016/0925-8388(95)02080-2

  • K. Koyama, H. Fujii and S. Suzuki .  Magnetic properties of interstitially modified compounds Sm3(Fe,M)29Zx (M=Ti, V, Cr and Z=H or N) .  J. Magn. Magn. Mater.161   118 - 126   1996Magnetic properties of interstitially modified compounds Sm3(Fe,M)29Zx (M=Ti, V, Cr and Z=H or N)Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)  

  • H. Fujii, K. Tatami and K. Koyama .  Nitrogenation process in Sm2Fe17 under various pressures up to 6 MPa .  J. Alloys and Compounds236   156 - 164   1996Nitrogenation process in Sm2Fe17 under various pressures up to 6 MPaReviewed

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    Language:English   Publishing type:Research paper (scientific journal)  

  • K. Koyama, H. Fujii and P.C. Canfield .  Magnetocrystalline anisotropy of Nd2Fe17 single crystal .  Physica B226   363 - 369   1996Magnetocrystalline anisotropy of Nd2Fe17 single crystalReviewed

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    Language:English   Publishing type:Research paper (scientific journal)  

  • K. Koyama, Y. Mori, M. Asano, T. Kamimori, H. Tange and M. Goto .  Effect of nitrogenation on magnetism for Y2Fe17-x(Si,Al)x .  J. Magn. Magn. Mater.140-144   969 - 970   1995Effect of nitrogenation on magnetism for Y2Fe17-x(Si,Al)xReviewed

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    Language:English   Publishing type:Research paper (scientific journal)  

  • T. Kamimori, K. Koyama and M. Goto .  Magnetocrystalline anisotropy of Y2Fe17 with silicon and carbon .  Nuclear Instruments and Methods in Physics Research B76   57 - 58   1993Magnetocrystalline anisotropy of Y2Fe17 with silicon and carbonReviewed

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    Language:English   Publishing type:Research paper (scientific journal)  

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Books

  • クレーンゲームで学ぶ物理学

    小山 佳一

    集英社インターナショナル  2024  ( ISBN:9784797681390

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    Language:Japanese

    CiNii Books

  • 強磁場X線回折実験によるMn2Sb0.95Ge0.05の磁場中結晶評価

    若森太音、廣井政彦、 三井好古、 高橋弘紀、 梅津理恵、小山佳一( Role: Joint author)

    東北大学金属材料研究所附属強磁場超伝導材料研究センター平成28年度年次報告書   2017.6 

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    Total pages:2   Language:Japanese Book type:Report

  • ビスマスの強磁場中示差熱分析分析

    三井好古、麓秀斗、 高橋弘紀、 小山佳一( Role: Joint author)

    東北大学金属材料研究所附属強磁場超伝導材料研究センター平成28年度年次報告書   2017.6 

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    Total pages:2   Language:Japanese Book type:Report

  • 強磁性体MnBiの反応焼結過程に対する磁場効果

    宮﨑泰樹、 三井好古、 梅津理恵、 高橋弘紀、宇田聡、小山佳一( Role: Joint author)

    東北大学金属材料研究所附属強磁場超伝導材料研究センター平成28年度年次報告書   2017.6 

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    Total pages:2   Language:Japanese Book type:Report

  • 焼酎酵母菌の磁場中培養

    小林領太, 三井好古, 伊藤昌和, 高橋弘紀, 高峯和則,小山佳一( Role: Joint author)

    東北大学金属材料研究所附属強磁場超伝導材料研究センター平成28年度年次報告書   2017.6 

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    Total pages:2   Language:Japanese Book type:Report

  • Cr基三元化合物CrAlGeの強磁性

    吉永総志, 三井好古, 梅津理恵, 木村尚次郎、小山佳一( Role: Joint author)

    東北大学金属材料研究所附属強磁場超伝導材料研究センター平成27年度年次報告書   2016.6 

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    Total pages:2   Language:Japanese Book type:Report

  • 強磁場中急冷炉の開発と性能評価

    山下美咲, アベ松賢一, 高橋弘紀, 三井好古, 小山佳一( Role: Joint author)

    東北大学金属材料研究所附属強磁場超伝導材料研究センター平成27年度年次報告書   2016.6 

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    Total pages:2   Language:Japanese Book type:Report

  • Bi-Mn固相焼結に対する組織観察

    高木観雄, 三井好古, 宮崎泰樹, 梅津理恵, 高橋弘紀, 小山佳一( Role: Joint author)

    東北大学金属材料研究所附属強磁場超伝導材料研究センター平成27年度年次報告書   2016.6 

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    Total pages:2   Language:Japanese Book type:Report

  • 焼酎酵母菌の増殖に対する磁場効果

    小林領太、三井好古、伊藤昌和、高橋弘紀、高峯和則、小山佳一( Role: Joint author)

    東北大学金属材料研究所附属強磁場超伝導材料研究センター平成27年度年次報告書   2016.6 

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    Total pages:2   Language:Japanese Book type:Report

  • 強磁場中におけるBi-Mn合金の巨視的変化の観察

    宮崎泰樹, 三井好古, アベ松賢一, 高橋弘紀, 宇田聡, 渡辺和雄, 小山佳一( Role: Joint author)

    東北大学金属材料研究所附属強磁場超伝導材料研究センター平成27年度年次報告書   2016.6 

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    Total pages:2   Language:Japanese Book type:Report

  • メタ磁性体MnCo0.92Fe0.08Ge化合物の磁気と構造特性

    大園康介、三井好古、廣井政彦、梅津理恵、高橋弘紀,松林和幸、上床美也、小山佳一( Role: Joint author)

    東北大学金属材料研究所附属強磁場超伝導材料研究センター平成27年度年次報告書   2016.6 

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    Total pages:2   Language:Japanese Book type:Report

  • ハーフメタル型ホイスラー合金と超伝導体のフルエピタキシャル多層膜の輸送特性

    重田出, 窪田崇秀, 桜庭裕弥, 木村尚次郎, 小山佳一, 淡路智, 高梨弘毅, 廣井政彦( Role: Joint author)

    東北大学金属材料研究所附属強磁場超伝導材料研究センター平成26年度年次報告書   2015.6 

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    Total pages:2   Language:Japanese Book type:Report

  • Fe-Si-B-P-Cuアモルファス合金の結晶化における強磁場効果

    小野寺礼尚, 木村尚次郎, 渡辺和雄, 横山嘉彦, 牧野彰宏、小山佳一( Role: Joint author)

    東北大学金属材料研究所附属強磁場超伝導材料研究センター平成26年度年次報告書   2015.6 

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    Total pages:2   Language:Japanese Book type:Report

  • 磁性材料の強磁場中熱分析と形態その場同時観測

    小山佳一、宮崎泰樹、三井好古、高橋弘紀、渡辺和雄、宇田聡( Role: Joint author)

    平成26年度東北大学金属材料研究所研究部共同研究報告書  2015.6 

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    Total pages:2   Language:Japanese Book type:Report

  • Fe-Si-B-P-Cuアモルファス合金の結晶化における強磁場効果

    小野寺礼尚, 木村尚次郎, 渡辺和雄, 横山嘉彦, 牧野彰宏、小山佳一( Role: Joint author)

    東北大学金属材料研究所附属強磁場超伝導材料研究センター平成26年度年次報告書   2015.6 

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    Total pages:2   Language:Japanese Book type:Report

  • 強磁性MnBiの磁場中固相反応焼結過程

    三井好古,梅津理恵,渡辺和雄,小山佳一( Role: Joint author)

    東北大学金属材料研究所附属強磁場超伝導材料研究センター平成26年度年次報告書   2015.6 

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    Total pages:2   Language:Japanese Book type:Report

  • 強磁場中液相焼結によるMnBi の磁気特性

    アベ松賢一,三井好古,梅津理恵,高橋弘紀,小山佳一( Role: Joint author)

    東北大学金属材料研究所附属強磁場超伝導材料研究センター平成26年度年次報告書   2015.6 

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    Total pages:2   Language:Japanese Book type:Report

  • Mn-Biの拡散挙動における強磁場の影響

    梅津理恵, 三井好古,小山佳一,高橋弘紀,渡邉和雄( Role: Joint author)

    東北大学金属材料研究所附属強磁場超伝導材料研究センター平成26年度年次報告書   2015.6 

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    Total pages:2   Language:Japanese Book type:Report

  • FeRh1-xCoxの磁気相転移

    大武和樹,小野寺礼尚,三井好古,高橋弘紀,木村尚次郎,渡辺和雄, 小山佳一( Role: Joint author)

    東北大学金属材料研究所附属強磁場超伝導材料研究センター平成26年度年次報告書   2015.6 

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    Total pages:2   Language:Japanese Book type:Report

  • MnCo0.92Fe0.08Ge 合金の強磁場X線回折測定による磁場誘起マルテンサイト変態の観測

    大園康介, 三井好古, 高橋弘紀, 梅津理恵, 廣井政彦, 松林和幸, 上床美也, 小山佳一( Role: Joint author)

    東北大学金属材料研究所附属強磁場超伝導材料研究センター平成26年度年次報告書   2015.6 

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    Total pages:2   Language:Japanese Book type:Report

  • 強磁場下における高Fe濃度アモルファス合金の結晶化挙動

    小野寺礼尚、木村尚次郎、渡辺和雄、横山嘉彦、牧野彰宏、小山佳一( Role: Joint author)

    東北大学金属材料研究所強磁場超伝導材料研究センター平成25年度年次報告書  2014.6 

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    Language:Japanese Book type:Report

  • Mn基磁性材料の強磁場中合成

    三井好古、梅津理恵、渡辺和雄、小山佳一( Role: Joint author)

    東北大学金属材料研究所強磁場超伝導材料研究センター平成25年度年次報告書  2014.6 

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    Language:Japanese Book type:Report

  • FeRhの強磁場・高温中磁化測定

    大武和樹、小野寺礼尚、三井好古、高橋弘紀、木村尚次郎、渡辺和雄、小山佳一( Role: Joint author)

    東北大学金属材料研究所強磁場超伝導材料研究センター平成25年度年次報告書  2014.6 

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    Language:Japanese Book type:Report

  • 極低温・強磁場下トンネル分光測定によるハーフメタル物質のスピン分極特性の解明

    重田出、窪田崇秀、桜庭裕弥、木村尚次郎、小山佳一、淡路智、高梨弘毅、廣井政彦( Role: Joint author)

    東北大学金属材料研究所強磁場超伝導材料研究センター平成25年度年次報告書  2014.6 

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    Language:Japanese Book type:Report

  • 磁場中における Mn2-xNi1+xZ (Z = Sb, Ga, Sn) の電気的および磁気的特性

    吉峰裕貴、廣井政彦、三井好古、木村尚次郎、小山佳一( Role: Joint author)

    東北大学金属材料研究所強磁場超伝導材料研究センター平成25年度年次報告書  2014.6 

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    Language:Japanese Book type:Report

  • 強磁場中液相焼結による MnBi の作製と特性

    アベ松賢一、三井好古、梅津理恵、高橋弘紀、小山佳一( Role: Joint author)

    東北大学金属材料研究所強磁場超伝導材料研究センター平成25年度年次報告書  2014.6 

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    Language:Japanese Book type:Report

  • 強磁場中熱分析・溶解その場観測装置の開発

    宮崎泰樹, 三井好古, アベ松賢一,前田健作, 高橋弘紀, 小山佳一, 宇田聡 渡辺和雄( Role: Joint author)

    東北大学金属材料研究所強磁場超伝導材料研究センター平成25年度年次報告書  2014.6 

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    Language:Japanese Book type:Report

  • Magnetic properties of Mn2Sb1-xZx (Z = Ge, Sn)

    K. Koyama, D. Shimada, H. Orihashi, D. Mitsunaga, M. Hiroi, K. Matsubayashi, Y. Uwatoko, R. Onodera, S. Kimura, and K. Takahashi( Role: Joint author)

    Rep. Fac. Sci., Kagoshima Univ.  2013.12 

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    Language:English Book type:Report

  • 強磁場下におけるMn2Sb1-ySny("0.08?y?0.15" )の特性

    島田大輔,折橋広樹,満永大輔,廣井政彦,小野寺礼尚,高橋弘紀,小山佳一( Role: Joint author)

    東北大学金属材料研究所強磁場超伝導材料研究センター平成24年度年次報告書  2013.6 

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  • 強磁場中溶解・合成のその場観察装置の開発

    三井好古,宮崎泰樹,前田健作,高橋弘紀,小山佳一,宇田聡,渡辺和雄( Role: Joint author)

    東北大学金属材料研究所強磁場超伝導材料研究センター平成24年度年次報告書  2013.6 

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    Language:Japanese Book type:Report

  • Nd-Fe-Co-B系急冷薄帯の強磁場中結晶化

    加藤宏朗,小山佳一,高橋弘紀( Role: Joint author)

    東北大学金属材料研究所強磁場超伝導材料研究センター平成24年度年次報告書  2013.6 

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    Language:Japanese Book type:Report

  • Fe基アモルファス合金の磁場中等温結晶化挙動

    小野寺礼尚,木村尚次郎,渡辺和雄,横山嘉彦,牧野彰宏,小山佳一( Role: Joint author)

    東北大学金属材料研究所強磁場超伝導材料研究センター平成24年度年次報告書  2013.6 

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  • Fe-C二元合金の磁場中状態図に関する研究

    吉澤清文,高橋弘紀,渡辺和雄,宮本吾郎,古原忠,小山佳一( Role: Joint author)

    東北大学金属材料研究所強磁場超伝導材料研究センター平成24年度年次報告書  2013.6 

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    Language:Japanese Book type:Report

  • 極低温・強磁場下トンネル分光測定によるハーフメタル物質のスピン分極特性の解明

    重田出,桜庭裕弥,木村尚次郎,小山佳一,高梨弘毅,廣井政彦( Role: Joint author)

    東北大学金属材料研究所強磁場超伝導材料研究センター平成24年度年次報告書  2013.6 

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    Language:Japanese Book type:Report

  • FeRhの磁場誘起相転移に関する研究

    大武和樹,小野寺礼尚,三井好古,高橋弘紀,木村尚次郎,渡辺和雄,小山佳一( Role: Joint author)

    東北大学金属材料研究所強磁場超伝導材料研究センター平成24年度年次報告書  2013.6 

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    Language:Japanese Book type:Report

  • 磁場中熱処理によるケイ素鋼の磁化方向の制御

    保科栄宏、原川俊郎、白石隆、高橋弘紀、小山佳一( Role: Joint author)

    ケーヒン技報  2013.1 

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    Language:Japanese Book type:Report

  • ホイスラー合金Mn2-xNi1+xSbの強磁場中電気的および磁気的特性

    満永大輔、折橋広樹、島田大輔、廣井政彦、高橋弘紀、小山佳一( Role: Joint author)

    東北大学金属材料研究所強磁場超伝導材料研究センター平成23年度年次報告書  2012.6 

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  • 強磁場X線回折実験によるMn1.8Co0.2Sbの磁場中結晶評価

    折橋広樹、満永大輔、廣井政彦、三井好古、高橋弘紀、渡辺和雄、小山佳一( Role: Joint author)

    東北大学金属材料研究所強磁場超伝導材料研究センター平成23年度年次報告書  2012.6 

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  • マンガン酸化物の凍結した相分離状態の圧力効果

    猪股佑、大内修也、松川倫明、 小山佳一 小林典男、 二森茂樹、 R.Suryanarayanan( Role: Joint author)

    東北大学金属材料研究所強磁場超伝導材料研究センター平成22年度年次報告書  2011.8 

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  • 磁性金属ガラスの結晶化における磁場効果

    小野寺礼尚、高橋弘紀、木村尚次郎、李相旻、横山嘉彦、牧野彰宏、渡辺和雄、小山佳一( Role: Joint author)

    東北大学金属材料研究所強磁場超伝導材料研究センター平成22年度年次報告書  2011.8 

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  • Fe-C 二元合金の強磁場中示差熱分析

    小山佳一、池原佑基、高橋弘紀、木村尚次郎、渡辺和雄( Role: Joint author)

    東北大学金属材料研究所強磁場超伝導材料研究センター平成22年度年次報告書  2011.8 

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  • 強磁場中示差熱分析測定による Mn-Bi 二元系の強磁場中平衡状態図の作成

    三井好古、渡辺 和雄、小山佳一、及川勝成( Role: Joint author)

    東北大学金属材料研究所強磁場超伝導材料研究センター平成22年度年次報告書  2011.8 

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  • Ni-Nb-Zr-H 系金属ガラスの電子輸送現象

    福原幹夫、吉田肇、小山佳一、井上明久、三浦良雄( Role: Joint author)

    東北大学金属材料研究所強磁場超伝導材料研究センター平成22年度年次報告書  2011.8 

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  • PrPd2Si2 単結晶の高磁場磁化過程

    繁岡透、崔菁蔚、藤原 哲也、木村 尚次郎、小山 佳一、渡辺 和雄( Role: Joint author)

    東北大学金属材料研究所強磁場超伝導材料研究センター平成22年度年次報告書  2011.8 

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  • 強磁場X線粉末カメラの評価

    三井好古、高橋弘紀、渡辺和雄、小山佳一( Role: Joint author)

    東北大学金属材料研究所強磁場超伝導材料研究センター平成21年度年次報告書  2010.6 

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  • Lu2Fe16.5Ru0.5金属間化合物の結晶構造と磁歪特性

    E.A. Tereshina, A.V. Andreev, 渡辺和雄、小山佳一( Role: Joint author)

    東北大学金属材料研究所強磁場超伝導材料研究センター平成21年度年次報告書  2010.6 

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  • 強磁場先端材料合成を目指した20テスラ級強磁場下示差熱分析

    小山佳一、池原祐基、三井好古、高橋弘紀、渡辺和雄( Role: Joint author)

    東北大学金属材料研究所強磁場超伝導材料研究センター平成21年度年次報告書  2010.6 

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  • 電子ジャーナルの利用について

    小山佳一( Role: Sole author)

    日本金属学会会報まてりあ  2005 

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MISC

  • 強磁場によるMn<sub>2</sub>NiGaの相分離

    齊藤光将, 小林領太, 三井好古, 梅津理恵, 伊東航, 高橋弘紀, 小山佳一

    日本金属学会九州支部・日本鉄鋼協会九州支部・軽金属学会九州支部合同学術講演大会講演概要集   2023   2023

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  • Magnetic properties of Cr-based itinerant ferromagnetic compounds

    三井好古, 吉田健斗, 小林領太, 小山佳一, 梅津理恵

    東北大学金属材料研究所新素材共同研究開発センター共同利用研究報告書(CD-ROM)   2019   2020

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  • Crystal structure of Fe<sub>1.3</sub>Mn<sub>1.7</sub>Si in magnetic fields

    三井好古, 廣井政彦, 野々山智仁, 高橋弘紀, 小山佳一

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2019   2020

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  • Magnetic field effects on gas-solid reaction for rare earth magnets

    尾上昌平, 三井好古, 小林領太, 高橋弘紀, 小山佳一

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2019   2020

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  • Synthesis of ferromagnetic phase of Mn<sub>53</sub>Zn<sub>2</sub>Al<sub>45</sub> by in-field annealing

    三井好古, 小林領太, 梅津理恵, 高橋弘紀, 水口将輝, 小山佳一

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2019   2020

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  • Magnetic properties of Ni<sub>2</sub>MnAl annealed in magnetic field

    三井好古, 小林領太, 梅津理恵, 高橋弘紀, 小山佳一

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2019   2020

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  • Fe-Ga合金の拡散・相形成における磁場効果

    小山佳一, 萩尾聡明, 三井好古, 高橋弘紀

    材料とプロセス(CD-ROM)   32 ( 1 )   2019

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  • Sm<sub>2</sub>Fe<sub>17</sub>N<sub>x</sub>(0≦x<3)の窒化合成及び熱分解過程における磁場効果

    尾上昌平, 小林領太, 三井好古, 梅津理恵, 上床美也, 小山佳一

    日本金属学会講演概要(CD-ROM)   164th   2019

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  • τ相の相安定に対する磁場効果

    小林領太, 三井好古, 及川勝成, 小野寺礼尚, 高橋弘紀, 小山佳一

    応用物理学会春季学術講演会講演予稿集(CD-ROM)   66th   2019

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  • Magnetic properties of Mn<sub>2-x</sub>Fe<sub>x</sub>Sb<sub>1-y</sub>Sn<sub>y</sub>(0.05≤x≤0.1, 0.05 ≤y≤0.1)

    Koyama Keiichi, Nwodo Adline N., Kobayashi Ryota, Mitsui Yoshifuru, Hiroi Masahiko, Takahashi Kohki, Umetsu Rie Y., Uwatoko Yoshiya

    Meeting Abstracts of the Physical Society of Japan   74.1 ( 0 )   1058 - 1058   2019

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    DOI: 10.11316/jpsgaiyo.74.1.0_1058

  • Magnetic properties of Cu<sub>2</sub>MnAl annealed under high magnetic fields

    三井好古, 中川駿, 小林領太, 梅津理恵, 高橋弘紀, 小山佳一

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2018   2019

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  • 強磁性Mn-Alの相平衡に対する磁場効果

    小林領太, 三井好古, 及川勝成, 小野寺礼尚, 梅津理恵, 高橋弘紀, 小山佳一

    日本金属学会九州支部・日本鉄鋼協会九州支部・軽金属学会九州支部合同学術講演大会講演概要集   2019   2019

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  • Differential Thermal Analysis in Mn-Al alloys

    小山佳一, 麓秀斗, 小林領太, 三井好古, 高橋弘紀

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2018   2019

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  • MnCoGe合金における熱処理効果

    野口滉平, 小林領太, 三井好古, 梅津理恵, 上床美也, 小山佳一

    日本金属学会九州支部・日本鉄鋼協会九州支部・軽金属学会九州支部合同学術講演大会講演概要集   2019   2019

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  • Mn<sub>2-x</sub>Fe<sub>x</sub>Sb<sub>1-y</sub>Sn<sub>y</sub>(0.05≦x≦0.1,0.05≦y≦0.1)の磁気相転移

    小山佳一, NWODO Adline N., 小林領太, 三井好古, 廣井政彦, 高橋弘紀, 梅津理恵, 上床美也

    日本物理学会講演概要集(CD-ROM)   74 ( 1 )   2019

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  • Evaluation of magnetic field effects on synthesis of ferromagnetic materials

    小林領太, 高永悠大, 三井好古, 高木観雄, 小山佳一, 高橋弘紀, 梅津理恵, 水口将輝

    東北大学金属材料研究所新素材共同研究開発センター共同利用研究報告書(CD-ROM)   2018   2019

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  • Magnetic properties of (Mn,Zn)-Al alloys obtained by in-field annealing

    三井好古, 高木観雄, 小林領太, 小山佳一, 梅津理恵, 高橋弘紀, 水口将輝

    東北大学金属材料研究所新素材共同研究開発センター共同利用研究報告書(CD-ROM)   2017   2018

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  • Mn-Al-Znに対する磁場中熱処理効果

    小林領太, 高木観雄, 三井好古, 梅津理恵, 高橋弘紀, 水口将輝, 小山佳一

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2017   2018

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  • Mn-Al合金の強磁場中熱分析

    三井好古, 麓秀斗, 小林領太, 高橋弘紀, 小山佳一

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2017   2018

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  • 巨大磁気熱量効果を示すFe基化合物の遍歴電子メタ磁性転移の温度依存性

    藤枝俊, 木村尚次郎, 高橋弘紀, 三井好古, 小山佳一, 深道和明, 鈴木茂

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2017   2018

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  • 強磁場X線回折実験によるMn<sub>1.9</sub>Fe<sub>0.1</sub>Sb<sub>0.9</sub>Sn<sub>0.1</sub>の磁場中結晶評価

    小山佳一, NWODO Adline N., 小林領太, 三井好古, 廣井政彦, 高橋弘紀, 梅津理恵, 上床美也

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2017   2018

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  • 磁場中固相-気相反応熱処理装置の開発

    尾上昌平, 小林領太, 三井好古, 小山佳一, 梅津理恵, 上床美也

    日本磁気科学会年会プログラム・要旨集   13th   2018

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  • 焼酎酵母菌の磁場中振盪培養

    小林領太, 三井好古, 高橋弘紀, 高峯和則, 小山佳一

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2017   2018

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  • Cr基三元化合物CrAl<sub>1+x</sub>Ge<sub>1-x</sub>の圧力下で抑制された強磁性

    増満勇人, 吉永総志, 三井好古, 小山佳一, 梅津理恵, 郷地順, 上床美也

    日本磁気科学会年会プログラム・要旨集   13th   2018

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  • Magnetic properties of Mn<sub>2</sub>Sb<sub>1-x</sub>Ge<sub>x</sub> (x=0.05,0.08,0.1) under high pressures

    小山佳一, 島田大輔, 安達義也, 三井好古, 廣井政彦, 上床美也

    鹿児島大学理学部紀要(Web)   50   2017

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  • ビスマスの強磁場中示差熱分析

    三井好古, 麓秀斗, 高橋弘紀, 小山佳一

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2016   2017

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  • 巨大磁気熱量効果を示すFe基化合物のメタ磁性転移と結晶構造

    藤枝俊, 三井好古, 小山佳一, 深道和明, 鈴木茂

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2016   2017

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  • 強磁場X線回折実験によるMn<sub>2</sub>Sb<sub>0.95</sub>Ge<sub>0.05</sub>の磁場中結晶評価

    若森太音, 廣井政彦, 三井好古, 高橋弘紀, 梅津理恵, 小山佳一

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2016   2017

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  • 磁場中酵母菌増殖観察装置の作製

    小林領太, 三井好古, 伊藤昌和, 高橋弘紀, 高峯和則, 小山佳一

    応用物理学会秋季学術講演会講演予稿集(CD-ROM)   78th   2017

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  • Magnetic properties of as-melt Mn-Al alloys annealed in magnetic field

    三井好古, 小林領太, 小山佳一, 梅津理恵, 高橋弘紀, 水口将輝

    東北大学金属材料研究所新素材共同研究開発センター共同利用研究報告書(CD-ROM)   2016   2017

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  • Mn<sub>1-x</sub>Cr<sub>x</sub>AlGe(0≦x≦1.0)の結晶構造及び磁気特性

    増満勇人, 吉永総志, 三井好古, 梅津理恵, 廣井政彦, 上床美也, 小山佳一

    日本金属学会九州支部・日本鉄鋼協会九州支部・軽金属学会九州支部合同学術講演大会講演概要集   2017   2017

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  • Magnetic Field Effects on the Morphology of Bi-Mn alloy prepared by solid-phase reactive sintering

    TAKAKI Akio, MITSUI Yoshifuru, MIYAZAKI Daiki, Y UMETSU Rie, TAKAHASHI Koki, KOYAMA Keiichi

    49   17 - 21   2016.12

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    CiNii Books

    Other Link: http://hdl.handle.net/10232/00029384

  • Magnetic Properties of MnCo_{1−x}Fe_{x}Ge (x = 0.08, 0.12)

    尾上 昌平, 大園 康介, 三井 好古, 廣井 政彦, 梅津 理恵, 上床 美也, 小山 佳一

    鹿児島大学理学部紀要 = Reports of the Faculty of Science, Kagoshima University   49   11 - 15   2016.12

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    Magnetization and Mössbauer spectroscopy measurements were performed for MnCo_{1−x}Fe_{x}Ge (x = 0.08, 0.12) to clarify its fundamental properties of the magnetism. The magnetic moments m for x = 0.08 was estimated to be 3.70 μB/f.u. at 10 K. The compound showed a first-order magnetic transition (FOMT) from the martensitic phase with high magnetic moment to the parent phase with low magnetic moment in the vicinity of Tt = 275 K with increasing temperature under magnetic field of μ0H = 1 T. From Mössbauer measurement for x = 0.12, the valence of Fe atom was found to be Fe2+. The obtained results were discussed on the basis of the mean-field calculation for the parent and martensitic phases.

    CiNii Books

  • Magnetic and transport properties of half-metallic Heusler alloy Co<sub>2</sub>Fe<sub>x</sub>Mn<sub>1-x</sub>Si/ superconductor NbN thin films

    Shigeta Iduru, Kubota Takahide, Makise Kazumasa, Kimura Shojiro, Awaji Satoshi, Shinozaki Bunju, Terada Norio, Koyama Keiichi, Takanashi Koki, Hiroi Masahiko

    Meeting Abstracts of the Physical Society of Japan   71   874 - 874   2016

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    DOI: 10.11316/jpsgaiyo.71.2.0_874

  • 19aPS-93 Magnetic field controlling the composition and decomposition process for ferromagnetic MnBi

    Koyama K., Miyazaki D., Mitsui Y., Takahashi K., Uda S.

    Meeting Abstracts of the Physical Society of Japan   71.1 ( 0 )   1098 - 1098   2016

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    DOI: 10.11316/jpsgaiyo.71.1.0_1098

    CiNii Books

  • 19pBC-13 Differential conductance properties for fully-epitaxial junctions of Heusler alloy Co_2FeSi and superconductor NbN

    Shigeta I., Kubota T., Sakuraba Y., Molenaar C. G., Beukers J. N., Kimura S., Golubov A. A., Brinkman A., Koyama K., Awaji S., Takanashi K., Hiroi M.

    Meeting Abstracts of the Physical Society of Japan   71.1 ( 0 )   1126 - 1126   2016

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    DOI: 10.11316/jpsgaiyo.71.1.0_1126

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  • メタ磁性体MnCo<sub>0.92</sub>Fe<sub>0.08</sub>Ge化合物の磁気と構造特性

    大園康介, 三井好古, 廣井政彦, 梅津理恵, 高橋弘紀, 松林和幸, 上床美也, 小山佳一

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2015   2016

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  • Magnetic properties of Mn-based magnetic materials prepared by in-field heat treatment

    三井好古, 小林領太, 小山佳一, 梅津理恵, 高橋弘紀, 水口将輝

    東北大学金属材料研究所新素材共同研究開発センター共同利用研究報告書   2015   2016

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  • 磁場を利用した強磁性材料の反応とその観察装置の開発 Invited Reviewed

    三井 好古, 小山 佳一

    日本材料科学会誌、材料の科学と工学   52 ( 5 )   15 - 18   2015.10

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  • ホイスラー化合物Ru<sub>2</sub>Cr<sub>1-x</sub>X<sub>x</sub>Si(X=V,Ti)の磁気および電気的性質

    廣井政彦, 佐野紘晃, 田底知也, 重田出, 伊藤昌和, 小山佳一, 真中浩貴, 寺田教男, 藤井宗明, 近藤晃弘, 金道浩一

    日本金属学会講演概要(CD-ROM)   157th   2015

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  • 21aPS-69 Magnetic Property and Pressure Effect of Mn_<2-x>Ni_<1+x>Ga

    Yoshimine Y., Mitsui Y., Hiroi M., Matsubayashi K., Uwatoko Y., Umetsu R., Koyama K.

    Meeting Abstracts of the Physical Society of Japan   70.1 ( 0 )   1003 - 1003   2015

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    Language:Japanese   Publisher:The Physical Society of Japan  

    DOI: 10.11316/jpsgaiyo.70.1.0_1003

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  • 23pAD-13 Spin polarization of half-metallic Heusler alloys by the Andreev reflection method in fully-epitaxial junctions

    Shigeta I., Kubota T., Sakuraba Y., Molenaar C. G., Beukers J. N., Kimura S., Golubov A. A., Brinkman A., Koyama K., Awaji S., Takanashi K., Hiroi M.

    Meeting Abstracts of the Physical Society of Japan   70.1 ( 0 )   1208 - 1208   2015

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    DOI: 10.11316/jpsgaiyo.70.1.0_1208

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  • FeRh<sub>1-x</sub>Co<sub>x</sub>の磁気相転移

    大武和樹, 小野寺礼尚, 三井好古, 高橋弘紀, 木村尚次郎, 渡辺和雄, 小山佳一

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2014   2015

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  • MnCo<sub>0.92</sub>Fe<sub>0.08</sub>Ge合金の強磁場X線回折測定による磁場誘起マルテンサイト変態の観測

    大園康介, 三井好古, 高橋弘紀, 梅津理恵, 廣井政彦, 松林和幸, 上床美也, 小山佳一

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2014   2015

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  • Reaction of the ferromagnetic materials in magnetic field and the development of the system for observing the magnetic field effects

    52 ( 5 )   165 - 168   2015

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  • 16aPS-13 Observation of magnetic field induced martensitic transformation on MnCo0.92Fe0.08Ge

    Ozono K, Mitsui Y, Hiroi M, Koyama K, Umetsu R. Y, Matsubayashi K, Uwatoko Y

    Meeting Abstracts of the Physical Society of Japan   70   719 - 719   2015

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    DOI: 10.11316/jpsgaiyo.70.2.0_719

  • 21aBJ-5 Magnetization in high magnetic field and magnetic phase diagram of Ru_<2-x>Fe_xCrSi

    Hiroi M, Nishi R, Tazoko T, Sano H, Shigeta I, Ito M, Koyama K, Kondo A, Kindo K

    Meeting Abstracts of the Physical Society of Japan   70   982 - 982   2015

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  • 19aPS-118 Superconducting properties of superconductor NbN/ferromagnetic Heusler alloy Co_2MnSi thin films

    Shigeta I, Kubota T, Makise K, Kimura S, Awaji S, Koyama K, Shinozaki B, Takanashi K, Hiroi M

    Meeting Abstracts of the Physical Society of Japan   70   1469 - 1469   2015

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    DOI: 10.11316/jpsgaiyo.70.2.0_1469

  • 7aPS-89 Magnetic properties of MnCo_<1-x>Fe_xGe, (0≦x≦0.12)

    Ozono K., Mitsui Y., Hiroi M., Koyama K., Umetsu R. Y.

    Meeting abstracts of the Physical Society of Japan   69 ( 2 )   252 - 252   2014.8

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  • 10pBF-3 Transport properties of half-metallic Heusler alloy/superconductor fully-epitaxial trilayer films and junctions

    Shigeta I., Kubota T., Sakuraba Y., Kimura S., Awaji S., Koyama K., Takanashi K., Hiroi M.

    Meeting abstracts of the Physical Society of Japan   69 ( 2 )   317 - 317   2014.8

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  • 27aPS-128 Synthesis of MnBi in high magnetic field

    Mitsui Y., Umetsu R. Y., Watanabe K., Koyama K.

    Meeting abstracts of the Physical Society of Japan   69 ( 1 )   505 - 505   2014.3

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  • 27aPS-48 Magnetic States of Mn_2Sb-based Metamagnetic Materials under High Pressures

    Matsumoto Yoshihiro, Koyama Keiichi, Matsubayashi Kazuyuki, Uwatoko Yoshiya

    Meeting abstracts of the Physical Society of Japan   69 ( 1 )   485 - 485   2014.3

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  • 27aPS-39 Magnetization of Ru_<2-x>Fe_xCrSi in high magnetic field

    Hiroi M., Nishiinoue S., Shigeta I., Koyama K., Kondo A., Kindo K.

    Meeting abstracts of the Physical Society of Japan   69 ( 1 )   483 - 483   2014.3

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  • Thermal analysis in high magnetic field ?Magnetic field effect on phase equilibrium- Reviewed

    Y. Mitsui, K. Koyama, S. Awaji, K. Watanabe

    Teion Kogaku (J. Cryo. Super. Soc. Jpn.)   49 ( 1 )   11 - 18   2014.1

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  • Magneto-Transport Properties in the Heusler Compounds Ru<SUB>2-x</SUB>Fe<SUB>x</SUB>CrSi

    S. Nishiinoue, H. Suwa, I. Shigeta, M. Hiroi, K. Koyama, S. Kimura, K. Watanabe, M. Fujii

    JPS Conf. Proc.   3   017018-1-017018-6   2014

  • 磁場中におけるMn<sub>2-x</sub>Ni<sub>1+x</sub>Z(Z=Sb,Ga,Sn)の電気的および磁気的特性

    吉峰裕貴, 廣井政彦, 三井好古, 木村尚次郎, 小山佳一

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2013   2014

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  • Magneto-transport properties of the Heusler compounds Ru_<2-x>Fe_xCrSi

    Hiroi M., Nishiinoue S., Suwa H., Shigeta I., Koyama K., Kimura S., Watanabe K., Fujii M.

    Meeting abstracts of the Physical Society of Japan   68 ( 2 )   374 - 374   2013.8

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  • Transport properties of half-metallic Heusler alloy/superconductor junctions III

    Shigeta I., Sakuraba Y., Molenaar C. G., Beukers J. N., Kimura S., Golubov A. A., Brinkman A., Koyama K., Watanabe K., Takanashi K., Hiroi M.

    Meeting abstracts of the Physical Society of Japan   68 ( 2 )   399 - 399   2013.8

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  • Electronic and magnetic properties of Mn_2Sb modified with third elements

    Goto Jyunya, Kakimoto Takashi, Koyama Keiichi, Fujii Shinpei

    Meeting abstracts of the Physical Society of Japan   68 ( 2 )   378 - 378   2013.8

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  • 26aPS-35 Magnetic Relaxation of Mn_<2-x>Co_xSb under Pressure

    Orihashi Hiroki, Matsubayashi Kazuyuki, Uwatoko Yoshiya, Koyama Keiichi

    Meeting abstracts of the Physical Society of Japan   68 ( 1 )   506 - 506   2013.3

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  • 27aXA-13 Transport properties of half-metallic Heusler alloy/superconductor junctions II

    Shigeta I., Sakuraba Y., Molenaar C. G., Beukers J. N., Kimura S., Golubov A. A., Brinkman A., Koyama K., Watanabe K., Takanashi K., Hiroi M.

    Meeting abstracts of the Physical Society of Japan   68 ( 1 )   537 - 537   2013.3

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  • 26aPS-36 Magnetic and conduction characteristic of Mn_<2-x>Cu_xSb

    Matsumoto Y, Orihashi H, Matsubayashi K, Uwatoko Y, Koyama K

    Meeting abstracts of the Physical Society of Japan   68 ( 1 )   506 - 506   2013.3

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  • Electronic and magnetic properties of Mn_2Sb modified with third elements

    Goto Jyunya, Kakimoto Takashi, Koyama Keiichi, Fujii Shinpei

    Meeting Abstracts of the Physical Society of Japan   68.2.3 ( 0 )   378   2013

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    DOI: 10.11316/jpsgaiyo.68.2.3.0_378_2

  • Electronic and Magnetic Structures of Cobalt Substituted Mn<sub>2</sub>Sb

    Goto Junya, Kakimoto Takatoshi, Fujii Shinpei, Koyama Keiichi

    Journal of the Japan Institute of Metals and Materials   77 ( 10 )   461 - 465   2013

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      First-principles band-structure calculations have been carried out for CoMnSb and MnCoSb, where the Co atom is substituted for Mn(I) and Mn(II) in Mn<sub>2</sub>Sb, respectively. Among several magnetic structures, a ferromagnetic (F) state and a kind of antiferromagnetic (AF) state only converge. For both magnetic states, the Co atom energetically prefers the Mn(I) site to the Mn(II) site, and the magnetic moments of Co on Mn(I) have a parallel coupling with those of Mn(II). The lattice constant <i>c</i> (<i>a</i>) shrinks (expands) from F to AF states. These are in good agreement with experimental trends. Furthermore, our result shows that the optimization of the ratio <i>c/a</i> (lattice distortion) is crucial to determine a preferable magnetic order and that the optimization of the atomic positions of Mn(II) and Sb is also crucial.<br>

    DOI: 10.2320/jinstmet.jaw201303

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  • Mn<sub>2-X</sub>Cu<sub>x</sub>Sbの強磁場下における磁気特性及び電気的特性

    松本佳大, 折橋広樹, 廣井政彦, 小山佳一, 松林和幸, 上床美也

    日本金属学会講演概要(CD-ROM)   153rd   2013

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  • 18aPSA-15 Mn_2Sb_<1-x>Ge_x(0.05&pre;x&pre;0.2)磁気特性(18aPSA 領域3ポスターセッション(量子スピン・フラストレーション・遍歴・f電子・酸化物・化合物磁性),領域3(磁性,磁気共鳴))

    島田 大輔, 折橋 広樹, 満永 大輔, 廣井 政彦, 小山 佳一, 松林 和幸, 上床 美也, 小野寺 礼尚, 高橋 弘紀

    日本物理学会講演概要集   67 ( 2 )   381 - 381   2012.8

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  • 18pCC-10 High field magnetization of the S=1/2 quasi 1 D lsing-like anitiferromagnet BaCo_2V_2O_8 in transverse fields II

    Kimura S., Watanabe K., Okunishi K., Hagiwara M., Kindo K., He Z., Taniyama T., Itoh M., Koyama K.

    Meeting abstracts of the Physical Society of Japan   67 ( 2 )   396 - 396   2012.8

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  • 18aPSA-5 Properties of the Heusler compounds Ru_2CrSi in megnetic field

    Hiroi M., Uchida K., Shigeta I., Ito M., Koyama K., Kimura S., Watanabe K.

    Meeting abstracts of the Physical Society of Japan   67 ( 2 )   379 - 379   2012.8

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  • 20pCC-12 Magnetization and spin polarization of Co_<2-x>Fe_xMnSi Heusler alloys

    Shigeta I., Sakuraba Y., Kimura S., Koyama K., Watanabe K., Hiroi M., Takanashi K.

    Meeting abstracts of the Physical Society of Japan   67 ( 2 )   434 - 434   2012.8

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  • 24aPS-47 圧力下磁化測定によるMn_<2-x>Co_xSbのカイネティックアレスト効果の研究(24aPS 領域3ポスターセッション,領域3(磁性,磁気共鳴))

    折橋 広樹, 小山 佳一, 松林 和幸, 上床 美也

    日本物理学会講演概要集   67 ( 1 )   486 - 486   2012.3

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  • Bi-Mn二元系の強磁場中平衡状態の計算

    三井好古, 小山佳一, 及川勝成, 渡辺和雄

    応用物理学関係連合講演会講演予稿集(CD-ROM)   59th   2012

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  • Magnetic properties of Mn<sub>2-x</sub>Co<sub>x</sub>Sb (x=0.17,0.2) under high magnetic fields

    折橋広樹, 満永大輔, 廣井政彦, 三井好古, 高橋弘紀, 渡辺和雄, 松林和幸, 上床美也, 小山佳一

    鹿児島大学理学部紀要(Web)   45   2012

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  • 強磁場X線回折実験によるMn<sub>1.8</sub>Co<sub>0.2</sub>Sbの磁場中結晶評価

    折橋広樹, 満永大輔, 廣井政彦, 三井好古, 高橋弘紀, 渡辺和雄, 小山佳一

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2011   2012

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  • Mn<sub>2</sub>Sb<sub>1-x</sub>Ge<sub>x</sub>(0.05≦x≦0.2)の強磁場下磁気特性

    島田大輔, 折橋広樹, 満永大輔, 伊藤昌和, 廣井政彦, 小山佳一, 小野寺礼尚, 高橋弘紀, 松林和幸, 上床美也

    日本金属学会講演概要(CD-ROM)   151st   2012

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  • Mn<sub>2-x</sub>Co<sub>x</sub>Sbの磁気緩和

    折橋広樹, 小山佳一, 松林和幸, 上床美也

    日本金属学会講演概要(CD-ROM)   151st   2012

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  • Mn<sub>2-x</sub>Co<sub>x</sub>Sbの圧力下磁化測定

    折橋広樹, 小山佳一, 松林和幸, 上床美也

    日本金属学会講演概要(CD-ROM)   150th   2012

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  • 23pGP-12 Magnetic anomaly in high magnetic field

    Ito M., Ogawa T., Urakawa S., Koyama K., Watanabe K., Kondo A., Kindo K.

    Meeting abstracts of the Physical Society of Japan   66 ( 2 )   444 - 444   2011.8

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  • Mn-Bi2元系状態図の熱力学的解析

    及川勝成, 三井好古, 三井好古, 安斎浩一, 小山佳一

    日本金属学会講演概要(CD-ROM)   149th   2011

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  • Mn-Bi二元系の強磁場中平衡状態

    三井好古, 池原佑基, 渡辺和雄, 小山佳一, 及川勝成, CHOI Eun Sang, PALM Eric

    日本金属学会講演概要   148th   2011

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  • Mn-Bi二元系の強磁場中平衡状態図の作成

    三井好古, 小山佳一, 及川勝成, 渡辺和雄

    応用物理学会学術講演会講演予稿集(CD-ROM)   72nd   2011

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  • 24aPS-8 Effect of pressure on field-induced step like transition of cubic manganite (Eu,Sr)MnO_3

    Iomata T., Yamato Y., Matsukawa M., Kobayashi S., kobayasi N., Oyama K.

    Meeting abstracts of the Physical Society of Japan   65 ( 2 )   555 - 555   2010.8

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  • 25pWP-6 MnBiの45T定常強磁場下示差熱分析(25pWP 酸化物・化合物磁性,領域3(磁性,磁気共鳴))

    小山 佳一, 三井 好古, 池原 佑基, 渡辺 和雄, Choi E. S., Palm E.

    日本物理学会講演概要集   65 ( 2 )   426 - 426   2010.8

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  • Cu添加Ni‐Mn‐In強磁性形状記憶合金の強磁場下磁気特性

    鹿又武, 遠藤慶太, 畠山和也, 伊東航, 梅津理恵, 貝沼亮介, 小山佳一, 渡辺和雄, 西原弘訓

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2009   89 - 91   2010.6

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  • Ni‐Mn基合金の磁場誘起相変態とメタ磁性形状記憶効果

    大塚誠, 小山佳一

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2009   135 - 137   2010.6

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  • High field magnetization processes in rare-earth sesquisulphides α-R<SUB>2</SUB>S<SUB>3</SUB> (R: rare earth) (2)

    戎修二, 小山佳一, 小北正徳, 堀越達彦, 河内良行, 谷村知紀, 永田正一

    東北大学金属材料研究所強磁場超伝導材料研究センター平成21年度年次報告   平成21年度   94 - 97   2010.6

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  • メタ磁性形状記憶合金Ni(Co)MnZ(Z=In,Sn,Al)の強磁場中磁化過程に関する研究

    石田清仁, 貝沼亮介, 梅津理恵, 伊東航, 小山佳一

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2009   79 - 81   2010.6

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  • 20aPS-35 Magnetoelasticity of Lu_2Fe_<17>-based intermetallics

    Tereshina E. A., Koyama K., Andreev A. V., Watanabe K., Ianard O.

    Meeting abstracts of the Physical Society of Japan   65 ( 1 )   456 - 456   2010.3

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  • 22pPSA-16 Magnetization Curves of TbZn_2

    Adachi Y., Kitai T., Kimura H., Koyama K., Yoshida H., Kaneko T.

    Meeting abstracts of the Physical Society of Japan   65 ( 1 )   501 - 501   2010.3

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  • 22pPSA-14 High-field cooling effect on the magnetization of α-Dy_2S_3

    Ebisu S., Koyama K., Horikoshi T., Kokita M., Nagata S.

    Meeting abstracts of the Physical Society of Japan   65 ( 1 )   501 - 501   2010.3

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  • 20pPSA-40 Effect of pressure on magnetic properties of electron-doped manganites Ca(Mn_<1-x>Sb_x)O_3

    Murano Y., Yamato Y., Matsukawa M., Kobayashi S, Kobayashi K., Koyama K., Nimori S.

    Meeting abstracts of the Physical Society of Japan   65 ( 1 )   573 - 573   2010.3

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  • 20aPS-59 Magnetization processes of DyPd_2Si_2 single crystal

    Cui J., Fujiwara T., Koyama K., Watanabe K., Uwatoko Y., Shigeoka T.

    Meeting abstracts of the Physical Society of Japan   65 ( 1 )   462 - 462   2010.3

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  • 45T中示差熱分析によるMnBiの強磁場中平衡状態

    三井好古, 池原佑基, 渡辺和雄, 小山佳一, 及川勝成, CHOI Eun Sang, PALM Eric

    日本磁気科学会年会プログラム・要旨集   5th   2010

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  • Decomposition Temperature of MnBi to 45 Tesla

    K. Koyama, Y. Mitsui, E.S. Choi, Y. Ikehara, K. Watanabe, E. Palm

    MAG LAB Reports, 2009 Science Highlights Special Edition   17 ( 2 )   30 - 31   2010

  • 強磁場中示差熱分析によるFe-C二元合金の高温・強磁場中特性評価

    池原佑基, 高橋弘紀, 渡辺和雄, 小山佳一, 古原忠, 宮本吾郎, 及川勝成, 原川俊郎, 保科栄宏, 長岡隆弘

    日本磁気科学会年会プログラム・要旨集   5th   2010

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  • NiCoMnGaメタ磁性形状記憶合金におけるカイネティックアレスト現象

    許きょう, 伊東航, 梅津理恵, 小山佳一, 貝沼亮介, 石田清仁

    日本金属学会講演概要   145th   411   2009.9

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  • Ni‐Mn‐In合金スパッタ膜の構造と磁気特性に及ぼすCo添加の影響

    大塚誠, 梅津理恵, 貝沼亮介, 三井好古, 小山佳一, 渡辺和雄, 石田清仁

    日本金属学会講演概要   145th   410   2009.9

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  • 25pPSA-49 High field magnetization processes of TbPd_2Si_2

    Shigeoka T., Fujiwara T., Koyama K., Watanabe K., Uwatoko Y.

    Meeting abstracts of the Physical Society of Japan   64 ( 2 )   349 - 349   2009.8

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  • 27pQJ-9 MnBiの2OT超強磁場中示差熱分析(遍歴磁性,領域3,磁性,磁気共鳴)

    小山 佳一, 池原 佑基, 三井 好古, 渡辺 和雄

    日本物理学会講演概要集   64 ( 2 )   376 - 376   2009.8

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  • 26aPS-51 Effect of Mn site substitution on magnetic properties of electron-dope manganites

    Murano Y., Saito T., Yamato Y., Matsukawa M., Kobayashi S., Kobayashi K., Koyama K., Nimori S.

    Meeting abstracts of the Physical Society of Japan   64 ( 2 )   489 - 489   2009.8

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  • 強磁場・高温X線回折測定によるNiCoMnIn薄膜の相変態の観測

    三井好古, 小山佳一, 渡辺和雄, 大塚誠, 梅津理恵, 貝沼亮介

    日本物理学会講演概要集   64 ( 2 )   377   2009.8

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  • Direct Measurement of Reversible Magnetic-Field-Induced Strain in Ni-Mn-Co-In Metamagnetic Shape Memory Alloys

    BASARAN B, ITO W, UMETSU R.Y, KARAMAN I, KAINUMA R, KOYAMA K, ISHIDA K

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2008   97 - 105   2009.6

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  • ナノポーラス金の電気伝導と磁気抵抗

    藤田武志, QIAN L.H, CHEN M.W, 岡田宏成, 小山佳一, 渡辺和雄, 前川禎通

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2008   141 - 142   2009.6

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  • 27aPS-102 The Origin of the Positive High-Field Shift of ^<59>Co NMR in a Ferromagnetic Co-based Heusler Alloys

    Furutani Y., Nishihara H., Kanomata T., Kobayashi K., Kainuma R., Ishida K., Koyama K., Watanabe K.

    Meeting abstracts of the Physical Society of Japan   64 ( 1 )   437 - 437   2009.3

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  • 28aTG-9 Bose-Einstein Condensation of Pb_2V_3O_9 Single Crystal Probed by Specific Heat and Magnetization Measurements

    Kawamata T., Uesaka M., Sugawara N., Sato M., Kaneko N., Koyama K., Kudo K., Kobayashi N., Koike Y.

    Meeting abstracts of the Physical Society of Japan   64 ( 1 )   474 - 474   2009.3

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  • 27pPSA-31 Nonlinear conduction and magnetoresistance effect of (La_<0.4>,Pr_<0.6>)_<1.2>Sr_<1.8>Mn_2O_7

    Yamato Y., Matsukawa M., Murano Y., Kumagai T., Koyama K., Kobayashi N., Nimori S., Suryanarayanan R.

    Meeting abstracts of the Physical Society of Japan   64 ( 1 )   574 - 574   2009.3

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  • 27aPS-119 Magnetization and Crystalline Electric Field Effect of NdCu_4Ag

    Adachi Y., Ito S., Inoue M., Kato H., Kitai T., Shigeoka T., Koyama K., Yoshida H., Kaneko T.

    Meeting abstracts of the Physical Society of Japan   64 ( 1 )   441 - 441   2009.3

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  • 27aPS-118 Development of a magnetometer under low temperature and high magnetic fields produced by the 28T-hybrid magnet

    Koyama K., Sakakura R., Watanabe K.

    Meeting abstracts of the Physical Society of Japan   64 ( 1 )   441 - 441   2009.3

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  • 29pTF-7 Performance test of high-field X-ray powder diffraction camera

    Mitsui Y., Koyama K., Takahashi K., Watanabe K., Fujita A.

    Meeting abstracts of the Physical Society of Japan   64 ( 1 )   505 - 505   2009.3

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  • 700K対応強磁場・高温X線回折測定用試料電気炉の製作

    三井好古, 小山佳一, 渡辺和雄

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2008   2009

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  • Research of magnetic anisotropy and coercivity in Nd-Fe-B sintered magnets

    2009   98 - 101   2009

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  • Superconductivity and coulomb oscillation in Ni-Nb-Zr-H glassy alloys with nanoclusters

    2009   138 - 140   2009

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  • 強磁場X線粉末カメラの開発

    三井好古, 小山佳一, 高橋弘紀, 渡辺和雄, 藤田麻哉

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2008   2009

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  • Unusual electrical characteristics in Heusler compounds Ru2CrGe and Ru2CrSn

    岡田 宏成, H. Okada, Y. Kusakari, E. Matsuoka, H. Onodera, K. Koyama, K. Watanabe, T. Kanomata

    J. Phys. Conf. Ser.   150   042153   2009

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  • Development of high-coercivity rare-earth permanent magnets by high-magnetic-field process

    2009   149 - 151   2009

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  • NiCoMnInメタ磁性形状記憶合金のマルテンサイト変態における異常

    伊東航, 梅津理恵, 伊藤恒平, 小山佳一, 藤田麻哉, 貝沼亮介, 石田清仁

    日本金属学会日本鉄鋼協会両東北支部研究発表大会   7th   35   2008.11

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  • 強磁場・高温X線回折測定を用いた磁場誘起構造相転移の観測

    三井好古, 小山佳一, 渡辺和雄, 梅津理恵, 貝沼亮介, 伊東航, 石田清仁

    日本磁気科学会年次大会プログラム・要旨集   3rd   29 - 30   2008.10

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  • Ni<sub>50</sub>Mn<sub>34</sub>In<sub>16</sub>合金の強磁場中磁化測定

    梅津理恵, 伊東航, 伊藤恒平, 小山佳一, 藤田麻哉, 及川勝成, 鹿又武, 貝沼亮介, 石田清仁

    日本金属学会講演概要   143rd   400   2008.9

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  • 20pPSA-4 Effect of electric current on steplike magnetostriction of (La_<0.4>, Pr_<0.6>)_<1.2>Sr_<1.8>Mn_2O_7

    Yamato Y., Kumagai T., Matsukawa M., Koyama K., Kobayashi N., Nimori S., Suryanarayanan R.

    Meeting abstracts of the Physical Society of Japan   63 ( 2 )   459 - 459   2008.8

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  • 23aQG-7 Development of an X-ray powder diffraction camera in high magnetic fields

    Koyama K., Mitsui Y., Takahashi K., Watanabe K.

    Meeting abstracts of the Physical Society of Japan   63 ( 2 )   431 - 431   2008.8

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  • 21pPSB-49 Development of an X-ray diffraction system in high magnetic field and high temperature

    Mitsui Y., Koyama K., Watanabe K.

    Meeting abstracts of the Physical Society of Japan   63 ( 2 )   414 - 414   2008.8

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  • 21pPSA-39 The Origin of the Positive Hyperfine Field at ^<59>Co in a Ferromagnetic Heusler Alloy Co_2VGa

    Nishihara H., Furutani Y., Kanomata T., Kobayashi K., Kainuma R., Ishida K., Koyama K., Watanabe K.

    Meeting abstracts of the Physical Society of Japan   63 ( 2 )   394 - 394   2008.8

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  • Ni‐Mn‐X(X=In,Sn)基メタ磁性形状記憶合金の基礎物性調査

    石田清仁, 貝沼亮介, 梅津理恵, 伊東航, 小山佳一

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2007   78 - 80   2008.6

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  • バルク金属複合ガラスの電気伝導メカニズム

    藤田武志, WANG Ke, CHEN M. W, 岡田宏成, 小山佳一

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2007   160 - 161   2008.6

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  • High-field control of independent magnetic-phase transitions on two kinds of different sites of rare-earth magnetic semiconductors (2)

    戎修二, 小山佳一, 表晴貴, 永田正一

    東北大学金属材料研究所強磁場超伝導材料研究センター平成19年度年次報告   平成19年度   59 - 61   2008.6

  • Ni‐Mn‐In新強磁性形状記憶合金の磁気特性

    安田泰士, 鹿又武, 貝沼亮介, 伊東航, 及川勝成, 石田清仁, 小山佳一, 渡辺和雄, 西原弘訓

    東北学院大学環境防災工学研究所紀要(CD-ROM)   ( 19 )   ROMBUNNO.2-3   2008.3

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  • 23aPS-55 Magnetic and transport properties of new Heusler compounds Ru_2CrGe and Ru_2CrSn

    Okada H., Kusakari Y., Matsuoka E., Onodera H., Koyama K., Watanabe K., Nishihara H., Kanomata T.

    Meeting abstracts of the Physical Society of Japan   63 ( 1 )   438 - 438   2008.2

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  • 24aPS-39 crystalline (La_<0.4>,Pr_<0.6>)_<1.2>Sr_<1.8>Mn_2O_7 bilayered manganite

    Yamato Y., Kumagai T., Matsukawa M., Koyama K., Kobayashi N., Nimori S., Suryanarayanan R.

    Meeting abstracts of the Physical Society of Japan   63 ( 1 )   579 - 579   2008.2

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  • 23aPS-75 Magnetic properties of α-Nd_2S_3 and α-Sm_2S_3

    Ebisu S., Koyama K., Ueno Y., Omote H., Nagata S.

    Meeting abstracts of the Physical Society of Japan   63 ( 1 )   443 - 443   2008.2

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  • 23aPS-73 High field magnetization processes of HoRh_2Si_2 single crystal

    Shibasaki H., Fujiwara T., Koyama K., Watanabe K., Uwatoko Y., Shigeoka T.

    Meeting abstracts of the Physical Society of Japan   63 ( 1 )   442 - 442   2008.2

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  • 23aPS-65 Magnetic Structure of NdCu_4Ag

    Adachi Y., Kitai T., Yamaguchi Y., Koyama K., Yoshida H., Kaneko T.

    Meeting abstracts of the Physical Society of Japan   63 ( 1 )   440 - 440   2008.2

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  • 23aPS-63 Magnetic and structural properties of MnBi under high magnetic fields

    Koyama K., Mitsui Y., Watanabe K.

    Meeting abstracts of the Physical Society of Japan   63 ( 1 )   440 - 440   2008.2

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  • 26aWK-5 Magnetostriction in Mn_3CuN

    Asano Kazuko, Koyama Keiichi, Takenaka Koshi

    Meeting abstracts of the Physical Society of Japan   63 ( 1 )   502 - 502   2008.2

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  • 26aYB-10 Pressure effect on steplike magnetostriction of (La_<0.4>,Pr_<0.6>)_<1.2>Sr_<1.8>Mn_2O_7

    Yamato Y., Kumagai T., Matsukawa M., Koyama K., Kobayashi N., Nimori S., Suryanarayanan R.

    Meeting abstracts of the Physical Society of Japan   63 ( 1 )   642 - 642   2008.2

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  • 強磁場下におけるNiCoMnInメタ磁性形状記憶合金のマルテンサイト変態挙動

    伊東航, 梅津理恵, 伊藤恒平, 小山佳一, 藤田麻哉, 及川勝成, 渡辺和雄, 貝沼亮介, 鹿又武, 石田清仁

    日本物理学会講演概要集   63 ( 1 )   437 - 437   2008.2

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  • ホイスラー化合物での強磁性と反強磁性の競合

    広井政彦, 六角継美, 伊藤昌和, 重田出, 真中浩貴, 寺田教男, 左近拓男, 小山佳一, 中村慎太郎, 野島勉

    日本物理学会講演概要集   63 ( 1 )   2008

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  • 強磁場・高温X線回折装置の開発

    三井好古, 小山佳一, 渡辺和雄

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2007   2008

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  • Magnetostructural phase transitions of ferromagnetic shape memory alloy sputtered films

    2008   150 - 152   2008

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  • ホイスラー合金Fe<sub>2</sub>Mn<sub>1-X</sub>V<sub>X</sub>Siの強磁場磁性の研究

    左近拓男, 廣井政彦, 野島勉, 小山佳一, 渡辺和雄

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2007   2008

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  • NiCoMnInメタ磁性形状記憶合金におけるマルテンサイト変態の異常挙動

    伊東航, 梅津理恵, 伊藤恒平, 小山佳一, 藤田麻哉, 及川勝成, 渡辺和雄, 貝沼亮介, 石田清仁

    日本金属学会講演概要   141st   401   2007.9

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  • Magnetostructural Phase Transformations of Ferromagnetic Shape Memory Alloy Sputtered Films

    Makoto Ohtsuka, Jyunpei Sekino, Kimio Itagaki, Toshiyuki Takagi, Keiichi Koyama

    Selected Topics in 2006 Annual Report at Sendai   5   2007.9

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  • 21aPS-84 Pressure effect on steplike magnetostriction of (La_<0.4>,Pr_<0.6>)_<1.2>Sr_<1.8>Mn_2O_7

    Kumagai T., Yamato Y., Matsukawa M., Koyama K., Kobayashi N., Nimori S., Suryanarayanan R.

    Meeting abstracts of the Physical Society of Japan   62 ( 2 )   536 - 536   2007.8

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  • 23pWG-5 Steplike magnetostriction of single crystalline (La_<.4>, Pr_<0.6>)_<1.2>Sr_<1.8>Mn_2O_7 bilayered manganite

    Yamato Y., Kumagai T., Matsukawa M., Koyama K., Kobayashi N., Nimori S., Suryanarayanan R.

    Meeting abstracts of the Physical Society of Japan   62 ( 2 )   633 - 633   2007.8

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  • 22pWD-5 The multi-step metamagnetism of HoRh_2Si_2 single crystal

    Shibasaki H., Zhang Y., Fujiwara T., Koyama K., Watanabe K., Uwatoko Y., Shigeoka T.

    Meeting abstracts of the Physical Society of Japan   62 ( 2 )   489 - 489   2007.8

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  • 22aPS-4 Magnetization measurement of DyB_2C_2 under high pressure and high magnetic fields

    Koyama Keiichi, Watanabe Kazuo, Onodera Hideya

    Meeting abstracts of the Physical Society of Japan   62 ( 2 )   460 - 460   2007.8

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  • 21aWE-3 Physical properties of the Heusler compounds Ru_<2-x>Fe_xCrSi II

    Hiroi M., Rokkaku T., Shigeta I., Fujiwara T., Uwatoko Y., Sakon T., Koyama K., Nakamura S., Nojima T.

    Meeting abstracts of the Physical Society of Japan   62 ( 2 )   431 - 431   2007.8

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  • 21aPS-85 Pressure effect on thermal expansion and magnetization of CMR bilayered manganites

    Matsukawa M., Yamato Y., Kumagai T., Nimori S., Koyama K., Kobayashi N., Suryanarayanan R.

    Meeting abstracts of the Physical Society of Japan   62 ( 2 )   536 - 536   2007.8

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  • ナノポーラスAuの伝導現象

    岡田宏成, 藤田武志, QIAN L. H, 小山佳一, 渡辺和雄, CHEN M. W

    日本物理学会講演概要集   62 ( 2 )   969   2007.8

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  • ナノポーラス金の磁気抵抗効果

    岡田宏成, 小山佳一, 渡辺和雄, 藤田武志, QIAN L. H, CHEN M. W

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2006   150 - 153   2007.6

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  • 強磁性形状記憶合金スパッタ膜における磁気構造相変態の評価

    大塚誠, 関野淳平, 小山佳一

    東北大学金属材料研究所強磁場超伝導材料研究センター年次報告   2006   93 - 96   2007.6

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  • Ni<sub>45</sub>Co<sub>5</sub>Mn<sub>36.7</sub>In<sub>13.3</sub>メタ磁性形状記憶合金の巨大磁気抵抗効果

    伊東航, 梅津理恵, 伊藤恒平, 須藤祐司, 小山佳一, 及川勝成, 藤田麻哉, 貝沼亮介, 鹿又武, 石田清仁

    日本金属学会講演概要   140th   147   2007.3

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  • ホイスラー合金Ni‐Mn‐X(X=Sn,In)の強磁場物性

    小山佳一, 岡田宏成, 渡辺和雄, 安田泰士, 鹿又武, 貝沼亮介, 伊東航, 及川勝成, 石田清二

    日本金属学会講演概要   140th   147   2007.3

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  • 鉄添加Ni<sub>2</sub>MnGaスパッタ膜の形状記憶効果に及ぼす拘束時効処理の影響

    関野淳平, 大塚誠, 松本實, 高木敏行, 小山佳一, 板垣乙未生

    日本金属学会講演概要   140th   140   2007.3

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  • 18aPS-43 Magnetic properties of Ni-Mn-In based metamagnetic shape memory alloys

    Ito W, Umetsu R. Y, Sutou Y, Koyama K, Oikawa K, Kainuma R, Kanomata T, Ishida K

    Meeting abstracts of the Physical Society of Japan   62 ( 1 )   411 - 411   2007.2

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  • 19aPS-86 Single Crystal X-ray Diffraction Measurements of Spinel Sulfide CuV_2S_4

    Okada H., Koyama K., Kimura H., Noda Y., Watanabe K.

    Meeting abstracts of the Physical Society of Japan   62 ( 1 )   576 - 576   2007.2

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  • 19aPS-64 Pressure effect on magnetostriction and relaxation phenomena of bilayer manganite single-crystals

    Tamura A., Kumagai T., Yamato Y., Matsukawa M., Nakanishi Y., Kobayashi N., Koyama K., Nimori S., Suryanarayanan R.

    Meeting abstracts of the Physical Society of Japan   62 ( 1 )   570 - 570   2007.2

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