MODELS FOR SPIN-STATE TRANSITIONS IN SOLIDS

被引:19
作者
RAMASESHA, S [1 ]
RAMAKRISHNAN, TV [1 ]
RAO, CNR [1 ]
机构
[1] INDIAN INST TECHNOL,DEPT PHYS,KANPUR 208016,UTTAR PRADESH,INDIA
来源
JOURNAL OF PHYSICS C-SOLID STATE PHYSICS | 1979年 / 12卷 / 07期
关键词
D O I
10.1088/0022-3719/12/7/020
中图分类号
O469 [凝聚态物理学];
学科分类号
070205 ;
摘要
The model for spin-state transitions described by Bari and Sivardiere (1972) is static and can be solved exactly even when the dynamics of the lattice are included; the dynamic model does not, however, show any phase transition. A coupling between the octahedra, on the other hand, leads to a phase transition in the dynamical two-sublattice displacement model. A coupling of the spin states to the cube of the sublattice displacement leads to a first-order phase transition. The most reasonable model appears to be a two-phonon model in which an ion-cage mode mixes the spin states, while a breathing mode couples to the spin states without mixing. This model explains the non-zero population of high-spin states at low temperatures, temperature-dependent variations in the inverse susceptibility and the spin-state population ratio, as well as the structural phase transitions accompanying spin-state transitions found in some systems.
引用
收藏
页码:1307 / 1317
页数:11
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