論文 - 小山　佳一

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   2021年査読

　詳細を見る

記述言語：英語   出版者・発行元：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 Mn₅₃Zn₂Al₄₅ in magnetic fields up to 15 T. The in-field annealing for Zn-added sample accelerated the ε–τ transformation 16 times faster than Mn₅₅Al₄₅ at annealing temperature of 623 K. The reduction of magnetization after finishing ε–τ transformation was also more rapid than that of Mn₅₅Al₄₅. However, magnetic-field-induced acceleration of ε–τ phase transformation and suppression of precipitation of β-phase were observed for Zn-added alloy Mn₅₃Zn₂Al₄₅ 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 Mn₅₃Zn₂Al₄₅, more precisely control of annealing time is required for obtaining high fraction of ferromagnetic τ-phase.</p>

DOI： 10.2320/matertrans.MT-M2020235

Scopus

CiNii Research

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   2021年査読

　詳細を見る

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Alloys and Compounds  

In-field heat treatments of a solid-liquid Mn/Ga diffusion couple were conducted at 573 and 673 K with and without a magnetic field of 5 T to investigate magnetic field effects on the phase formation. Formation of the β-Mn, Mn3Ga, γ-MnGa, λ-MnGa, Mn2Ga5, and MnGa4 phases was observed. The obtained results indicated that the reaction and phase growth of λ-MnGa and Mn2Ga5 proceeded by diffusion-controlled process for both heat treatments at 0 and 5 T. We confirmed that a magnetic field suppressed the phase growth of λ-MnGa and Mn2Ga5. The parabolic coefficients of the λ-MnGa and Mn2Ga5 phases were exponentially suppressed by applying magnetic field of 5 T. It is suggested that gain of Zeeman energy of Mn-rich phase played a key role for the magnetic-field-induced suppression of the formation of the λ-MnGa and Mn2Ga5 phases.

DOI： 10.1016/j.jallcom.2021.161310

Scopus

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   2021年査読

　詳細を見る

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Magnetism and Magnetic Materials  

A magnetic field enhanced the decomposition of a Cu2MnAl Heusler alloy. An aging treatment at 573 K under 10 T promoted decomposition of a L21 phase and hard magnetic properties were exhibited. The crystallite size of the L21 phase decreased on annealing over 12 h and approached 22 nm at zero field. However, the crystallite size of the L21 phase of the 5 T-annealed sample was almost half that of the 0-T-annealed sample and decreased rapidly, indicating enhanced grain refinement by in-field annealing. Decomposition of the L21 phase was more pronounced in the 10-T-aged sample. The hysteresis loop for 10-T-aged sample had a large coercive force of 232 mT and a magnetization of 13 Am2/kg. These properties were markedly different from those of the 0-T-annealed sample. An increase of nucleation owing to a decrease of critical radius caused grain refinement associated with decomposition and magnetic hardening of Cu2MnAl.

DOI： 10.1016/j.jmmm.2021.168411

Scopus

Y. Mitsui, Y. Takanaga, R. Kobayashi, K. Koyama .  Effect of carbon addition on the phase stability of hcp-Mn-Al .  Physics B595   412379   2020年10月査読

　詳細を見る

記述言語：英語   掲載種別：研究論文（学術雑誌）  

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

その他リンク： 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年9月査読

　詳細を見る

記述言語：英語   掲載種別：研究論文（学術雑誌）  

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

その他リンク： https://www.sciencedirect.com/science/article/pii/S0925838820315565?via%3Dihub

Noguchi K., Mitsui Y., Hiroi M., Umetsu R.Y., Gouchi J., Uwatoko Y., Koyama K. .  Effects of Substituted Elements on Spin Reorientation in Mn[2-x]Fe[x]Sb[1-y]Sn[y] .  MATERIALS TRANSACTIONS61 ( 8 ) 1492 - 1495   2020年8月査読

　詳細を見る

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：公益社団法人 日本金属学会  

The spin reorientation and Curie temperature of Mn21xFexSb11ySny (0 ¯ x, y ¯ 0.15) compound were investigated by magnetization measurements. Spin reorientation temperature increased from 255 K at x = 0 to 383 K at x = 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 c-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 x 2 0.10 or T 2 300 K.

DOI： 10.2320/matertrans.mt-mn2019016

Scopus

CiNii Research

Koyama K., Onoue M., Kobayashi R., Mitsui Y., Umetsu R.Y., Uwatoko Y. .  Magnetic Field Effect on Nitrogenation of Sm₂Fe₁₇ .  MATERIALS TRANSACTIONS61 ( 8 ) 1487 - 1491   2020年8月査読

　詳細を見る

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：公益社団法人 日本金属学会  

Nitrogenation of Sm2Fe17 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 Sm2Fe17N2.9 was obtained at 743 K. Mössbauer spectroscopy results suggested that a 5-T magnetic field promoted the phase transformation to the fully-nitride Sm2Fe17N3 phase. The magnetic field effect was discussed based on the magnetic energy gain and magnetic properties of host Sm2Fe17 and fully nitride Sm2Fe17N3

DOI： 10.2320/matertrans.mt-mn2019012

Scopus

CiNii Research

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年8月査読

　詳細を見る

記述言語：英語   掲載種別：研究論文（学術雑誌）  

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

その他リンク： https://www.jstage.jst.go.jp/article/matertrans/61/8/61_MT-MN2019016/_article

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年8月査読

　詳細を見る

記述言語：英語   掲載種別：研究論文（学術雑誌）  

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

その他リンク： https://www.jstage.jst.go.jp/article/matertrans/61/8/61_MT-MN2019013/_article

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年8月査読

　詳細を見る

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本金属学会  

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

その他リンク： https://www.jstage.jst.go.jp/article/materia/59/8/59_422/_article/-char/ja/

Deguchi T., Matsubayashi K., Uwatoko Y., Koyama T., Kohara T., Nakamura H., Mitsui Y., Koyama K. .  Magnetic Measurements of Narrow-Gap Semiconductor FeSb₂ under High Pressure .  MATERIALS TRANSACTIONS61 ( 8 ) 1476 - 1479   2020年7月招待 査読

　詳細を見る

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：公益社団法人 日本金属学会  

Pressure effects on magnetic susceptibility» and energy gap Eg0 of narrow-gap semiconductor FeSb2 were investigated for the temperature range of 50300 K and pressures up to 13 kbar. The estimated Eg0 for ambient pressure, Eg0(0), was 29 meV. By application of pressure,» was suppressed, and Eg0(P) was estimated to be 52 meV for 13 kbar. The fourth-order expansion coefficient £ of the free energy in magnetization was positive and enhanced by applying pressures.

DOI： 10.2320/matertrans.mt-mn2019015

Scopus

CiNii Research

Tanaka A., Yoshinaga S., Mitsui Y., Sasaki H., Kanomata T., Koyama K. .  Magnetic Properties of Weak Itinerant Electron Ferromagnet Au₄V .  MATERIALS TRANSACTIONS61 ( 8 ) 1473 - 1475   2020年7月査読

　詳細を見る

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：公益社団法人 日本金属学会  

The magnetization measurements were carried out for polycrystalline Au4V in magnetic fields up to 130 kOe. The spontaneous magnetic moment ps was determined to be 0.255 ®B/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 TA = 1.3 © 103 K and T0 = 2.3 © 103 K using the data for 110130 kOe.

DOI： 10.2320/matertrans.mt-mn2019011

Scopus

CiNii Research

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年4月査読

　詳細を見る

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： https://doi.org/10.2355/isijinternational.ISIJINT-2019-470

その他リンク： https://www.jstage.jst.go.jp/article/isijinternational/60/4/60_ISIJINT-2019-470/_article

Noguchi K., Kobayashi R., Mitsui Y., Umetsu R., Gouchi J., Uwatoko Y., Koyama K. .  Heat treatment effect on the magnetic properties and martensitic transformations of MnCoGe .  Journal of Magnetism and Magnetic Materials499   2020年4月査読

　詳細を見る

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Magnetism and Magnetic Materials  

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

Scopus

濵﨑貢、⼭⼝光⾂、陳麗、⼩原益⼰、三井好古、⼩⼭佳⼀ .  光の回折と干渉の現象を調べる教材の開発と実験 .  鹿児島大学紀要52   7 - 14   2019年12月

　詳細を見る

記述言語：日本語   掲載種別：研究論文（大学，研究機関等紀要）  

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

機関リポジトリURL

その他リンク： http://hdl.handle.net/10232/00030849

Watanabe Y., Hagio T., Kobayashi R., Mitsui Y., Koyama K. .  Phase formation of a solid-liquid MnGA diffusion couple under a magnetic field .  MATERIALS TRANSACTIONS60 ( 10 ) 2195 - 2198   2019年10月査読

　詳細を見る

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：公益社団法人 日本金属学会  

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 MnGa3, Mn2Ga5, MnGa, Mn3Ga2 and ¢-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 Mn2Ga5 phases. The parabolic coefficients of MnGa and Mn2Ga5 for a zero magnetic field were determined as 8.7 © 10-3 µm2s-1 and 4.6 © 10-1 µm2s-1 respectively. For a magnetic field of 5 T, the parabolic coefficients were evaluated as 11 © 10-3 µm2s-1 for the MnGa phase and 4.5 © 10-1 µm2s-1 for the Mn2Ga5 phase.

DOI： 10.2320/matertrans.mt-maw2019013

Scopus

CiNii Research

Onoue M., Kobayashi R., Mitsui Y., Umetsu R., Uwatoko Y., Koyama K. .  In-Field Heat Treatment Effect on Nitridation of Sm₂Fe₁₇ .  MATERIALS TRANSACTIONS60 ( 10 ) 2179 - 2182   2019年10月査読

　詳細を見る

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：公益社団法人 日本金属学会  

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 Sm2Fe17 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 Sm2Fe17N2.9 was obtained at 743 K.

DOI： 10.2320/matertrans.mt-maw2019009

Scopus

CiNii Research

小林領太、三井好古、梅津理恵、高橋弘紀、水口将輝、小山佳一 .  磁場印加による強磁性 τ-Mn-Al への相変態の促進 .  日本金属学会誌83 ( 6 ) 181 - 185   2019年査読

　詳細を見る

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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   2019年査読

　詳細を見る

記述言語：英語   掲載種別：研究論文（学術雑誌）  

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   2019年査読

　詳細を見る

記述言語：英語   掲載種別：研究論文（学術雑誌）