Magnetic phase transition of the perovskite-type Ti oxides

被引：25

作者：

Mochizuki, M ^{[1
]}

Imada, M ^{[1
]}

机构：

[1] Univ Tokyo, Inst Solid State Phys, Kashiwa, Chiba 2778581, Japan

来源：

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN | 2000年 / 69卷 / 07期

关键词：

perovskite-type Ti oxides; GdFeO3-type distortion; d-level degeneracy; orbital ordering; second-order perturbation theory; A-type antiferromagnetism; Mermin and Wagner's theorem;

D O I：

10.1143/JPSJ.69.1982

中图分类号：

O4 [物理学];

学科分类号：

0702 ;

摘要：

The properties and mechanism of the magnetic phase transition of the perovskite-type Ti oxides, which is driven by the Ti-O-Ti bond angle distortion. are studied theoretically using the effective spin and pseudo-spin Hamiltonian with strong Coulomb repulsion. It is shown that the A-type antiferromagnetic (AFM(A)) to ferromagnetic (FM) phase transition occurs as the Ti-O-Ti bond angle is decreased. Through this phase transition, the orbital state is hardly changed so that the spin-exchange coupling along the c-axis changes nearly continuously from positive to negative and is approximately zero at the phase boundary. The resultant strong two-dimensionality in the spin coupling causes rapid suppression of the critical temperature, as observed experimentally.

引用

页码：1982 / 1985

页数：4