A simple theory of inhomogeneity linewidth broadening in Mn_xFe_3−x,O₄ ferrites

Abstract

A simple theory of linewidth broadening due to thermal treatment is given. The theory is based on the assumption that the manganese-rich regions — clusters — with local tetragonal symmetry appear in the sample due to the alignment of tetragonally distorted Mn^{3 +} ions. This is a source of local anisotropy fields, leading to two-magnon scattering. The size of clusters and consequently their contribution to the linewidth depends on the thermal treatment. The function giving the dependence of the linewidth broadening on the cluster size is calculated using Schlömann's autocorrelation function. The recent experimental results are qualitatively discussed in terms of this theory. For the temperature dependence of the effect an effective compositionx = 1·8 inside the cluster is assumed, which gives a qualitative agreement with experiment. The discussion of the dependence of linewidth broadening on the composition has only an illustrative character and shows that the theory is compatible with experiment. A qualitative disagreement found for the angular dependence of δ(ΔH) is believed to be a consequence of the high field approximation used.