Theoretical Model for Tetragonal-to-Cubic Phase Transformations in Transition Metal Spinels

Abstract

The origin of the large tetragonal distortions which occur in a number of transition metal oxides having the spinel structure has been examined recently by Dunitz and Orgel in terms of the crystal field theory. According to these authors the macroscopic distortions arise as a consequence of a Jahn-Teller type distortion in the immediate environment of certain transition metal ions. Thus, all the observed large distortions in spinels have been correlated with the results of this crystal field treatment on the basis of the spatial ordering of the local distortions.