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Spin Dynamics in Low Dimensional Quantum Spin System

Research Project

Project/Area Number 04640334
Research Category

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

Allocation TypeSingle-year Grants
Research Field 固体物性
Research InstitutionKYOTO UNIVERSITY

Principal Investigator

CHIBA Meiro  KYOTO UNIVERSITY, Institute of Atomic Energy, Assistant, 原子エネルギー研究所, 助手 (90027144)

Project Period (FY) 1992 – 1993
Project Status Completed (Fiscal Year 1993)
Budget Amount *help
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1993: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1992: ¥1,600,000 (Direct Cost: ¥1,600,000)
KeywordsLow Dimensional Magnetism / Quantum Spin Effect / Nuclear Magnetic Resonance / 低係元礒性体
Research Abstract

The quantum spin effect is one of the most interesting phenomena in the physics of the low dimensional magnetium. The study is focussed on the S=1 and S=1/2 quantum spin effects of the1D magnets through the experiments of NMR in high magnetic fields up to 15T.
1. S=1 Quantum Effect (Haldane Effect)
Haldane has predicted that in 1D Heisenberg antiferromagnet with integer spin the ground state is singlet. The prediction has given an impetus to experiments on S=1, quasi-1D antiferromagnets. Among several S=1 antiferromagnets, NENP [Ni(C_2H_8N_2)_2NO_2(CIO_4)] has been reported to be one of the best candidates to study the Haldane gap.
In NENP we have observed, even below the critical field (9.8T), a large transverse moment through the proton NMR experiment. We have attributed the transverse moment to the staggered moment induced by the cooperation of the field induced staggered field and the large staggered susceptibility. The appearance of the transverse staggered moment is not a property o … More f the Haldane state, but is peculiar to NENP where the local symmetry axis at the site of Ni^<2+> tilts from the crystalline axis. Thus, under the magnetic field the special attention must be paid to treat the spin states of NENP.Nevertheless, we found that the proton spin-lattice relaxation rate was still consistent with the Haldane gap.
2. S=1/2 Quantum Effect
In CsCuCl_3, one of the ABX_3-type triangular-lattice magnets, an anomalous jump of the magnetization has been reported in the ordered phase at the magnetic field around 12 T.The material is quasi-1D Heisenberg ferromagnet with S = 1/2. In the classical spin model such a magnetization jump can not be expected. A theoretical model has been proposed that the magnetization jump will appear through the transition of the spin structure caused by the quantum spin fluctuation.
We have observed through the NMR experiment a discontinuity in the spectrum of^<133>Cs at the magunetic field corresponding to the magnetization jump. The critical field was clear-cut and no hysteresis was observed for the sweep direction of the magnetic field. The discontinuity of the spectum can be analyzed as due to the abrupt change in the spin structure. The spectra above and below the critical field are compatible with the spin structure of the theoretical model. Less

Report

(3 results)
  • 1993 Annual Research Report   Final Research Report Summary
  • 1992 Annual Research Report
  • Research Products

    (9 results)

All Other

All Publications (9 results)

  • [Publications] 千葉明朗: "Successive Phase Transitions in CsNiBr_3 Observed by ^<133>Cs NMR Including Critical Examination of the Local Field" Journal of the Physical Society of Japan. 61. 1758-1771 (1992)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1993 Final Research Report Summary
  • [Publications] 千葉明朗: "Anomalous Spectrum of ^<133>Cs NMR in CsCu Cl_3 around the Applied Field 11T" Journal of the Physical Society of Japan. 62. 4186-4189 (1993)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1993 Final Research Report Summary
  • [Publications] 千葉明朗: "NMR Study of the Quantum Spin Effect of the 1D Magnet in High Magnetic Fields" Physica B. (印刷中). (1994)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1993 Final Research Report Summary
  • [Publications] M.Chiba, Y.Ajiro, H.Kikuchi, S.Maegawa and T.Morimoto: ""Successive Phase Transitions in CsNiBr_3 Observed by ^<133>Cs NMR Including Critical Examination of the Local Field"" J.Phys.Soc.Jpn.61. 1758-1771 (1992)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1993 Final Research Report Summary
  • [Publications] M.Chiba, K.Ohara, Y.Ajiro and T.Morimoto: ""Anomalous Spectrum of ^<133>Cs NMR in CsCuCl_3 around the Applied Field 11 T"" J.Phys.Soc.Jpn.62. 4186-4189 (1993)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1993 Final Research Report Summary
  • [Publications] M.Chiba, Y.Ajiro and T.Morimoto: ""NMR Study on the Quantum Spin Effect of the 1D Magnet in High Magnetic Fields"" Physica B. (in press). (1994)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1993 Final Research Report Summary
  • [Publications] 千葉明朗: "Anomalous Spectrum of ^<133>Cs NMR in CsCuCl_3 around the Applied Field 11 T" Journal of the Physical Society of Japan. 62. 4186-4189 (1993)

    • Related Report
      1993 Annual Research Report
  • [Publications] 千葉明朗: "NMR Study on the Quntum Spin Effect of the 1D Magnet in High Magnetic Fields" Physica B. (印刷中). (1994)

    • Related Report
      1993 Annual Research Report
  • [Publications] 千葉 明朗: "Successive Phase Transitions in CsNiBr_3 Observed by ^<133>Cs NMR lncluding Critical Examination of the Local Field" Journal of the Physicol Society of Japan. 61. 1758-1771 (1992)

    • Related Report
      1992 Annual Research Report

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Published: 1992-04-01   Modified: 2016-04-21  

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