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NEW IMPURITY ERRECTS IN ONE-DIMENSIONAL HEISENBERG ANTIFERROMANETS WITH A SPIN-SINGLET GROUND STATE

Research Project

Project/Area Number 09640418
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field 固体物性Ⅱ(磁性・金属・低温)
Research InstitutionCHIBA UNIVERSITY

Principal Investigator

ITOH Masayuki  CHIBA UNIVERSITY,FACULTY OF SCIENCE,ASSOCIATE PROFESSOR, 理学部, 助教授 (90176363)

Project Period (FY) 1997 – 1998
Project Status Completed (Fiscal Year 1998)
Budget Amount *help
¥3,800,000 (Direct Cost: ¥3,800,000)
Fiscal Year 1998: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1997: ¥3,200,000 (Direct Cost: ¥3,200,000)
Keywordssinglet ground state / one-dimensional antiferromagnet / quantum spin svstem / impurity effect / spin state / cgarge ordering / NMR / 核磁気緩和
Research Abstract

NMR studies were performed to clarify magnetic properties of magnets with a spin-singlet ground state, particularly, impurity effects in one-dimensional Heisenberg antiferromagnets. Our research results are summarized in the following.
1. NMR experiments on the Zn-doped spin-Peicris system Cu_<1-x>Zn_xGeO_3 were performed to study impurity effects in one-dimensional Heisenberg antiferromagnets. We compared experimental results of the Cu nuclear spin-lattice relaxation rate and the NMR line width with recent theoretical results and discussed the effects of the antiferromagnetic correlation on the spin dynamics in the Zn doped system.
2. Magnetic properties of LaCoO_3 and RCoO_3 (R= Pr, Nd, Sm and Eu) with a singlet ground state were investigated. We found that LaCoO_3 undergoes the spin-state transition from the low-spin state to the intermediate-spin state at about 100 K, whereas the low-spin state remains in RCoO_3 up to about 500 K where the metal-insulator transition takes place. This finding shows no relation between the spin state and the metal-insulator transition in these cobalt oxides. We also found that La_<2-x>Sr_xCoO_4 undergoes the spin state transition at a Sr concentration.
3. Based on V NMR results of vanadium oxides V_<2-y>O_3 and (V_<1-x>Ti_x)_2O_3, we found that a spin-gap behavior which leads to a non-magnetic state appears at low temperatures in the paramagnetic metallic state of these vanadium oxides.
4. Magnetic properties of vanadium bronzes A_xV_2O_3 (A=Na, Ca and Ag) with one-dimensional zigzag chains and a ladder were studied. We found that the charge ordering of V_<4+> and V5_<5+> sites in AV_6O_<15> (A_<0.33>V_2O_5) commonly takes places at a low temperature in AV_6O_<15>. The mixed-valence state in the high-temperature region and the gradual charge ordering in the charge-order state are new interesting problems in quantum spin systems with a particular geometrical structure.

Report

(3 results)
  • 1998 Annual Research Report   Final Research Report Summary
  • 1997 Annual Research Report
  • Research Products

    (12 results)

All Other

All Publications (12 results)

  • [Publications] M. Itoh et al.: "Spin-state transition and magnetic properties of LaCoO_3" Physica B. 230-232. 756-758 (1997)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1998 Final Research Report Summary
  • [Publications] K. Motoya et al.: "NMR and neutron scattering studies of metallic phase of (V_<1-x>Ti_x)_2O_3" J. Magn. Magn. Mater.177-181. 593-594 (1998)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1998 Final Research Report Summary
  • [Publications] M. Itoh et al.: "NMR study of the spin state of RCoO_3 (R=Pr, Nd, Sm, and Eu)" Physica B. 259-261. 902-903 (1999)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1998 Final Research Report Summary
  • [Publications] M. Itoh et al.: "NMR study of the spin state and magnetic properties of layered perovskite cobalt oxdies La_<2-x>Sr_xCoO_4" Physica B. 259-261. 997-998 (1999)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1998 Final Research Report Summary
  • [Publications] M.Itoh, M.Mori, M.Sugahara, T.Yamauchi and Y.Ueda: "Spin-state transition and microscopic magnetic properties of LaCoO_3" Physica B. 756. 230-232 (1997)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1998 Final Research Report Summary
  • [Publications] K.Motoya, K.Nakaguchi, A.Nakaju, K.Ishiguchi, T.Kawasaki, M.Itoh, Y.Ueda and S.Shin: "NMR and neutron scattering studies of metallic phase of(V_<1-x>Ti_x)_2O_3" J.Magn.Magn.Mater.593. 177-181 (1998)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1998 Final Research Report Summary
  • [Publications] M.Itoh, M.Mori, S.Yamaguchi and Y.Tokura: "NMR study of the spin state of RCoO_3(R=Pr, Nd, Sm, and Eu)" Physica B. 902. 259-261 (1999)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1998 Final Research Report Summary
  • [Publications] M.Itoh, M.Mori, Y.Moritomo, A.Nakamura: "NMR study of the spin state and magnetic properties of layered perovskite cobalt oxides La_<2-x>Sr_xCoO_4" Physica B. 997. 259-261 (1999)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1998 Final Research Report Summary
  • [Publications] M.Itoh: "NMR Study of the spin stute and magnetic properties of La_<2-x>Fr_xCoO_4" Physica B. (印刷中).

    • Related Report
      1998 Annual Research Report
  • [Publications] M.Itoh: "NMR study of the Spin state of RCoO_3(R=Pr,Nd,Sm,and Eu)" Physica B. (印刷中).

    • Related Report
      1998 Annual Research Report
  • [Publications] M.Itoh: "Spin-state transition and microscopic magnetic properties of LaCoO_3" Physica B. 230-232. 756-758 (1997)

    • Related Report
      1997 Annual Research Report
  • [Publications] K.Motoya: "NMR and neutron scattering studies of metallic state of(V_<1-X>Ti_X)_2O_3" J.Magn.Magn.Mater.177-181. (1998)

    • Related Report
      1997 Annual Research Report

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Published: 1997-04-01   Modified: 2020-05-15  

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