Study of spinels using the BPW method

Abstract

We present a study of a group of B-site spinel ferrimagnetic compounds having magnetic properties dominated by strong ferromagnetic interactions, using a modified Bethe-Peierls-Weiss (BPW) method. We obtain the exchange parameters by studying the transition temperature and the inverse susceptibility curves. We use a method for obtaining the exchange constants using the ratio between the transition temperatures obtained by the Weiss molecular field theory and a more advanced theory, such as high temperature expansion, and compare the ratio with the experimental data. We also study the inverse magnetic susceptibility curves which, for the case of dominant ferromagnetic interactions, are linear in the high temperature limit and have nonlinear behaviour near the transition temperature. In particular, we study systems such as MCr 2X 4, where M = Cd,Hg and X = S,Se, which are ferrimagnetic spinels, for which we find excellent fits to the experimental magnetic susceptibility data using the modified BPW method.