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1990 Fiscal Year Final Research Report Summary

Study of Magnetic Excitations in Random Systems

Research Project

Project/Area Number 01460038
Research Category

Grant-in-Aid for General Scientific Research (B)

Allocation TypeSingle-year Grants
Research Field 固体物性
Research InstitutionThe Institute of Physical and Chemical Research

Principal Investigator

KATSUMATA Koichi  RIKEN, Magnetic Materials Laboratory Principal Researcher, 磁性研究室, 主任研究員 (90002104)

Project Period (FY) 1989 – 1990
KeywordsRandom Magnetic System / Spin-glass / Diluted Magnet / Magnetic Excitation / Electron Spin Resonance / Quantum Spin System / 量子スピン系
Research Abstract

It is the aim of the present project to clarify the nature of magnetic excitations in random magnetic systems with competing spin anisotropies and with competing exchange interactions. The important findings obtained from this study are summarized below :
(1) The magnetic excitations in a randomly diluted XY antiferromagnet Mg_<1-x>Co_xCl_2 are studied by Electron Spin Resonance (ESR) technique. We have observed several ESR lines in the samples with x below the percolation concentration (x_p). One of them is interpreted as arising from Co^<2+> pair coupled by anisotropic exchange interaction. The others are interpreted as a uniform mode whose frequency vs. magnetic field relation is the same as that in the ordered phase with x above x_p.
(2) The magnetic excitation in a randomly diluted Ising antiferromagnet Mg_<1-x>Fe_xCl_2 are studied by ESR method. It is shown from the analysis of the result that both of the single ion anisotropy and the anisotropic exchange interaction contribute to the anisotropy energy of FeCl_2 with nearly the same amount.
(3) The magnetic excitations in the typical spin one linear chain Heisenberg antiferromagnet Ni (C_2H_8N_2) _2NO_2 (ClO_4) are studied in which some of the Ni atoms are randomly substituted for Cu. Novel ESR lines are observed and are analyzed by the following model. When Cu atoms are introduced into the valence-bond -solid ground state, spin 1/2 degrees of freedom in the Ni sites neighboring the Cu recover. We have calculated the excitation spectra of the weakly coupled three spin 1/2 system and have obtained a good agreement between the theory and the experiment.

  • Research Products

    (10 results)

All Other

All Publications (10 results)

  • [Publications] J. Tuchendler: "Magnetic Excitations in Random Systems in High Magnetic Fields" Physica. B155. 323-327 (1989)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 勝又 紘一: "Electron Spin Resonance of a Co^<2+> Pair in Mg_<1ーx>Co_xCl_2 Coupled by Anisotropic Exchange Interactions" Journal of Physics:Condenced Matter. 1. 10507-10514 (1989)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 勝又 紘一: "Magnetic Excitations in the Disordered System Mg_<1ーx>Co_xCl_2" Proc. “Relaxation in Complex Systems and Related Topics", Ed. I.A.Campbell and C.Giovannella (Plenum, New York). 67-70 (1990)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] J. Tuchendler: "Electron Spin Resonance in the Diluted Uniaxial Antiferromagnet Mg_<1ーx>Fe_xCl_2" Solid State Communications. 74. 1159-1163 (1990)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 萩原 政幸: "Observation of S=1/2 Degrees of Freedom in an S=1 Linear Chain Heisenberg Antiferromagnet" Physical Review Letters. 65. 3181-3184 (1990)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] J. Tuchendler and K. Katsumata: ""Magnetic Excitations in Random Systems in High Magnetic Fields"" Physica. B155. 323-327 (1989)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] K. Katsumata and J. Tuchendler: ""Electron Spin Resonance of a Co^<2+> Pair in Mg_<1-x>Co_xCl_2 Coupled by Anisotropic Exchange Interactions"" J. Phys. : Condens. Matter. 1. 10507-10514 (1989)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] K. Katsumata and J. Tuchendler: ""Magnetic Excitations in the Disordered System Mg_<1-x>Co_xCl_2"" Proc. Relarxation in Complex Systems and Related Topics, Ed. I. A. Campbell and C. Giovannella (Plenum, New York). 67-70 (1990)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] J. Tuchendler and K. Katsumata: ""Electron Spin Resonance in the Diluted Uniaxial Antiferromagnet Mg_<1-x>Fe_xCl_2" Solid State Commun. 74. 1159-1163 (1990)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] M. Hagiwara, K. Katsumata, I. Affleck, B. I. Halperin and J. P. Renard: ""Observation of S=1/2 Degrees of Freedom in an S=1 Linear-Chain Heisen-berg Antiferromagnet"" Phys. Rev. Lett. 65. 3181-3184 (1990)

    • Description
      「研究成果報告書概要(欧文)」より

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Published: 1993-08-12  

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