Cubic harmonic analysis of magnetic anisotropy measurements on single crystal Ho xTb 1−xFe 2 laves phase compounds

Abstract

Room temperature magnetic anisotropy measurements have been made on a series of low anisotropy Ho xTb 1−xFe 2 compounds, with 0.826 < x < 0.908, using torque magnetometry techniques. An analysis of the data using the conventional expansion of anisotropy energy in terms of the direction cosines proved inadequate because of the presence of higher order contributions to the anisotropy. When these contributions were included in the expansion, non unique anisotropy constants were obtained which were not consistent with the predictions of the single ion model. An analysis of the data using an expansion of the anisotropy in terms of an orthonormal set of functions, namely the cubic harmonics developed by Mueller and Priestly, proved more successful. The results showed that the two lowest order anisotropy constants, κ 4 and κ 6, both varied linearly with holmium concentrations as predicted by the single ion model; however, κ 8, the next higher order term, was not consistent with the predicted behavior. The origin of this contribution is believed to be related to the magnetostriction.