中国物理B ›› 2009, Vol. 18 ›› Issue (10): 4497-4505.doi: 10.1088/1674-1056/18/10/066

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Effects of anharmonic lattice distortion on orbital and magnetic orderings in KCuF3

邹良剑1, 陈东猛2, 刘大勇3   

  1. (1)Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, P. O. Box 1129, Hefei 230031, China; (2)Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, P. O. Box 1129, Hefei 230031, China;College of Physics Science and Technology, China University of Petroleum, Dongying 257061, China; (3)Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, P. O. Box 1129, Hefei 230031, China;Graduate School of the Chinese Academy of Sciences, Beijing 100049, China
  • 收稿日期:2009-02-11 修回日期:2009-02-28 出版日期:2009-10-20 发布日期:2009-10-20
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant Nos 90303013 and 10874186), the `100 Talents Project' and the Knowledge Innovation Program of the Chinese Academy of Sciences (CAS).

Effects of anharmonic lattice distortion on orbital and magnetic orderings in KCuF3

Liu Da-Yong(刘大勇)a)b), Chen Dong-Meng(陈东猛)a)c), and Zou Liang-Jian(邹良剑)a)†   

  1. a Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, P. O. Box 1129, Hefei 230031, China; b Graduate School of the Chinese Academy of Sciences, Beijing 100049, China; c College of Physics Science and Technology, China University of Petroleum, Dongying 257061, China
  • Received:2009-02-11 Revised:2009-02-28 Online:2009-10-20 Published:2009-10-20
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant Nos 90303013 and 10874186), the `100 Talents Project' and the Knowledge Innovation Program of the Chinese Academy of Sciences (CAS).

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摘要： Lattice, magnetic and orbital structures in KCuF3 are self-consistently determined by our cluster self-consistent field approach based on a spin-orbital-lattice Hamiltonian. Two stable structures are obtained and found to be degenerate, which confirms the presence of the coexistent phases observed experimentally. We clearly show that due to the inherent frustration, the ground state of the system only with the superexchange interaction is degenerate; while the Jahn--Teller distortion, especially the anharmonic effect, stabilizes the orbital ordered phase at about 23\% in the x2--y2 orbit and at 77\% in the 3z2--r2 orbit. Meanwhile the magnetic moment of Cu is considerably reduced to 0.56μB, and magnetic coupling strengths are highly anisotropic, Jz/Jxy \approx 18. These results are in good agreement with the experiments, implying that the anharmonic Jahn--Teller effect plays an essential role in stabilising the orbital ordered ground state of KCuF3.

Abstract: Lattice, magnetic and orbital structures in KCuF3 are self-consistently determined by our cluster self-consistent field approach based on a spin-orbital-lattice Hamiltonian. Two stable structures are obtained and found to be degenerate, which confirms the presence of the coexistent phases observed experimentally. We clearly show that due to the inherent frustration, the ground state of the system only with the superexchange interaction is degenerate; while the Jahn--Teller distortion, especially the anharmonic effect, stabilizes the orbital ordered phase at about 23% in the x2--y2 orbit and at 77% in the 3z2--r2 orbit. Meanwhile the magnetic moment of Cu is considerably reduced to 0.56μB, and magnetic coupling strengths are highly anisotropic, Jz/Jxy $\approx$ 18. These results are in good agreement with the experiments, implying that the anharmonic Jahn--Teller effect plays an essential role in stabilising the orbital ordered ground state of KCuF3.

Key words: orbital ordering, KCuF3, Jahn--Teller effect, anharmonic lattice distortion

中图分类号:  (Exchange and superexchange interactions)

  • 75.30.Et
71.15.Mb (Density functional theory, local density approximation, gradient and other corrections) 71.70.Ej (Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect) 75.30.Cr (Saturation moments and magnetic susceptibilities) 75.50.Ee (Antiferromagnetics)