中国物理B ›› 2009, Vol. 18 ›› Issue (10): 4497-4505.doi: 10.1088/1674-1056/18/10/066
邹良剑1, 陈东猛2, 刘大勇3
Liu Da-Yong(刘大勇)a)b), Chen Dong-Meng(陈东猛)a)c), and Zou Liang-Jian(邹良剑)a)†
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.
中图分类号: (Exchange and superexchange interactions)