研究者詳細 - 小山　佳一

論文 - 小山　佳一

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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年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：JAPAN INST METALS

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

Web of Science

Scopus

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年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：JAPAN SOC APPLIED PHYSICS

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

Web of Science

Scopus

H. Kato, M. Ishizone, K. Koyama, T. Miyazaki . Realization of anisotropic nanocomposite magnet in Nd<inf>2</inf>Fe <inf>14</inf>B/α-Fe thin films . Journal of Magnetism and Magnetic Materials290 1221 - 1225 2005年4月

記述言語：英語掲載種別：研究論文（学術雑誌）

A series of Nd2Fe14B/α-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. © 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmmm.2004.11.407

Web of Science

Scopus

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年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：JAPAN SOC APPLIED PHYSICS

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

Web of Science

Scopus

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年1月査読

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

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

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

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 2005年査読

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 2005年査読

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

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 2005年査読

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 2005年査読

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

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 2005年査読

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 2005年査読

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 2005年査読

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 2005年査読

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 2005年査読

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 2005年査読

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