Models for spin-state transitions in solids

Ramasesha, S. ; Ramakrishnan, T. V. ; Rao, C. N. R. (1979) Models for spin-state transitions in solids Journal of Physics C: Solid State Physics, 12 (7). pp. 1307-1317. ISSN 0022-3719

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Official URL: http://iopscience.iop.org/0022-3719/12/7/020

Related URL: http://dx.doi.org/10.1088/0022-3719/12/7/020

Abstract

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.

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Deposited On:13 May 2011 08:35
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