研究者詳細 - 小山　佳一

論文 - 小山　佳一

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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：IOP PUBLISHING LTD

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

Web of Science

Scopus

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年6月査読

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC 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 Neel temperature. In addition, ESR affected by hyperfine interaction was observed in GdBi.

Web of Science

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年5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：ELSEVIER SCIENCE BV

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

Web of Science

Scopus

T. Suzuki, H. Matsui, H. Tsuchiya, E. Negishi, K. Koyama, N. Toyota . Antiferromagnetic resonance in λ-(BEDT-TSF)<inf>2</inf>FeCl <inf>4</inf> . Synthetic Metals135 ( 1-3 ) 567 - 568 2003年4月

記述言語：英語掲載種別：研究論文（学術雑誌）

An antiferromagnetic resonance in λ-(BETS)2FeCl 4 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. © 2003 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0379-6779(02)00745-2

Web of Science

Scopus

H. Ohta, Y. Oshima, Y. Inagaki, S. Okubo, M. Kimata, K. Koyama, M. Motokawa, T. Mori . Magneto-optical measurements of β-(BEDT-TTF)<inf>2</inf>AuI <inf>2</inf> . Synthetic Metals135 ( 1-3 ) 527 - 528 2003年4月

記述言語：英語掲載種別：研究論文（学術雑誌）

Magneto-optical measurements of β-(BEDT-TTF)2AuI 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 H⊥ab-plane. Obtained effective mass was 0.9 mc 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. © 2003 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0379-6779(02)00718-X

Web of Science

Scopus

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年4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：ELSEVIER SCIENCE SA

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

Web of Science

Scopus

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年3月

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年3月

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年1月査読

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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

Web of Science

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 2003年査読

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

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 2003年査読

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年査読

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

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 2003年査読

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 2003年査読

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 2003年査読

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 2003年査読

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 2003年査読

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 2003年査読

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