Theoretical modelling of the effects of anisotropy and stress on the magnetization and magnetostriction of Tb0.3Dy0.7Fe2

Abstract

The alloy Tb0.3Dy0.7Fe2 is known to have a useful combination of high magnetostriction and low anisotropy energy. This means that relatively high strain amplitudes, exceeding 1 X 10(-3), can be obtained at low to moderate field strengths of less than 240 kA/m. This paper is concerned with the application of the anisotropic rotation model of the magnetization mechanism in this material. The model comprises the underlying assumptions which correspond to the Stoner-Wohlfarth model and its derivatives. In this case, the magnetic moments of the domains are constrained by the anisotropy to lie along the [111] directions within the crystal. It is shown from symmetry considerations that the fractional occupancies of six of the eight [111] directions exhibit pair degeneracy, leaving only five independent parameters to describe the distribution of domains among those directions. The changes in magnetization and magnetostriction which occur as the material is magnetized by a field along the [112] axis were determined both under zero stress and under a range of uniaxial stress levels applied along the [112] axis by following the changes in direction of the local minima in the sum of anisotropy, field and magnetostrictive energies.