Spin-wave theory of the magnetocrystalline anisotropy in gadolinium metal

Abstract

Magnetocrystalline anisotropy in gadolinium has been studied utilizing a spin-wave model in which a crystal field of hexagonal close-packed symmetry and magnetic dipole-dipole interactions are treated as a first-order perturbation to isotropic exchange. Corrections to the temperature dependence of K₁, due to normal and magnetostrictive thermal expansion, are shown to be small. The resulting agreement with the measurements of Graham and of Corner et al. for K₂(T), K₃(T), K₄(T) is good, but the temperature dependence of K₁ is anomalous. Crystal-field parameters, evaluated by comparison with experiment, are about 100 times larger than the corresponding parameters in gadolinium ethyl sulphate.