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2002 Fiscal Year Final Research Report Summary

Critical Phenomena and Dynamics of Orbital Degrees of Freedom

Research Project

Project/Area Number 12440092
Research Category

Grant-in-Aid for Scientific Research (B)

Allocation TypeSingle-year Grants
Section一般
Research Field 固体物性Ⅱ(磁性・金属・低温)
Research InstitutionTHE UNIVERSITY OF TOKYO (2002)
Tohoku University (2000-2001)

Principal Investigator

HIROTA Kazuma  Institute for Solid State Physics, Associate Professor, 物性研究所, 助教授 (90272012)

Project Period (FY) 2000 – 2002
KeywordsOrbital / Electric Quadrupole / Neutron Scattering / Resonant X-ray / Mn Perovskite Oxide / RB_2C_2 / Phase Separation / CeB_6
Research Abstract

We have studied (1) systems with orbital degrees of freedom which are strongly coupled to the other degrees of freedom - 3d transition metal oxides and (2) systems with orbital degrees of freedom which spontaneously order - 4f rare-earth metal compounds. As for (1), we have focused on layered Mn oxide La_<2-2x>Sr_<1+2x>Mn_2O_7. In 0.5 【less than or equal】 x 【less than or equal】 0.6, we have succeeded in growing single crystals with the FZ method, and found that an antiferromagnetic (AF) metallic state becomes stable with increasing the doping rate x. Our neutron scattering studies have revealed that the A-type AF metallic state and the CE-type AF charge-ordered state competitively coexist in an electronically phase separated state, which drastically changes with temperature and x. We have also employed other techniques such as resonant x-ray scattering, polarized neutron diffraction, magnetic Compton profile, spin wave measurement and analysis, and clarified quantitatively the orbital state and its effect to the magnetism and transport in 0.3 【less than or equal】 x 【less than or equal】 0.5.
As for (2), we have scrutinized the antiferro-quadrupole (AFQ) ordering process and structure in DyB_2C_2 by resonant x-ray scattering, which is the first example of resonant x-ray scattering measurement of AFQ state. We have also confirmed that HoB_2C_2 undergoes AFQ and AFM ordering below T_Q = 5.0 K, and found that there remains short-range magnetic correlations, well above T_Q, with an exotic incommensurate periodicity different from that of the low temperature state. We also revealed the details of AFQ ordering process and state hi CeB_6, known for a prototypical AFQ material for a long time, by resonant x-ray scattering.

  • Research Products

    (13 results)

All Other

All Publications (13 results)

  • [Publications] K.Hirota, T.Matsumura, Y.Endoh, et al.: "Direct Observation of Antiferroquadrupolar Ordering : Resonant X-ray Scattering Study of DyB_2C_2"Physical Review Letters. Vol.84,12. 2706-2709 (2000)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] M.Kubota, K.Hirota, Y.Endoh, et al.: "Relation between crystal and magnetic structures of layered manganite La_<2-2x>Sr_<1+2x>Mn_2O_7 (0.30 X 0.50)"Journal of the Physical Society of Japan. Vol.69,6. 1606-1609 (2000)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] D.E.Cox, K.Hirota, Y.Endoh, et al.: "Vertical boundary at x〜0.11 in the structural phase diagram of the La_<1-x>Sr_xMnO_3 system (0.08 x 0.125)"Physical Review B. Vol.64,2. 24431-1-24431-9 (2001)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] A.Koizumi, K.Hirota, et al.: "Study of the e_g Orbitals in the Bilayer Manganite La_<2-2x>Sr_<1+2x>Mn_2O_7 by using Magnetic Compton-Profile Measurement"Physical Review Letters. Vol.86. 5589-5592 (2001)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] T.Matsumura, K.Hirota, Y.Endoh, et al.: "Observation of the antiferroquadrupolar order in DyB_2C_2 by resonant x-ray scattering"Physical Review B. Vol.62,9. 094420-1-094420-11 (2002)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] K.Hirota, Y.Endoh, et al.: "Spin dynamical properties and orbital states of the layered perovskite La_<2-2x>Sr_<1+2x>Mn_2O_7 (0.3 x<0.5)"Physical Review B. Vol.65,6. 64414-1-64414-10 (2002)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 藤井保彦編(廣田和馬, 村上洋一他): "第5章 トピックス 放射光-中性子-電子線による軌道秩序の観測"実験物理学講座5:構造解析(丸善). 325-362 (2001)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] K. Hirota, T. Matsumura, Y. Endoh, et al.: "Direct Observation of Antiferroquadrupolar Ordering : Resonant X-ray Scattering Study of DyB_2C_2"Phys. Rev. Lett.. 84. 2706-2709 (2000)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] M. Kubota, K. Hirota, Y. Endoh, et al.: "Relation between crystal and magnetic structures of the layered manganites La_<2-2x>Sr_<1+2x>Mn_2O_7 (0.30 【less than or equal】 x 【less than or equal】 0.50)"J. Phys. Soc. Japan. 69. 1606-1609 (2000)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] D. E. Cox, K. Hirota, Y. Endoh, et al.: "Vertical boundary at x 【approximately equal】 0.11 in the structural phase diagram of the La_<1-x>Sr_xMnO_3 system (0.08 【less than or equal】 x 【less than or equal】 0.125)"Phys. Rev. B. 64. 024431-1-9 (2001)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] A. Koizumi, K. Hirota, et al.: "Study of the e_g Orbitals in the Bilayer Manganite La_<2-2x>Sr_<1+2x>Mn_2O_7 by using Magnetic Compton-Profile Measurement"Phys. Rev. Lett. 86. 5589-5592 (2001)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] T. Matsumura, K. Hirota, Y. Endoh, et al.: "Observation of the antiferroquadrupolar order in DyB_2C_2 by resonant x-ray scattering"Phys. Rev. B. 65. 094420-1-11 (2002)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] K. Hirota, Y. Endoh, et al.: "Spin dynamical properties and orbital states of the layered perovskite La_<2-2x>Sr_<1+2x>Mn_2O_7 (0.3 【less than or equal】 x 【less than or equal】 0.5)"Phys. Rev. B. 65. 064414-1-10 (2002)

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

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Published: 2004-04-14  

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