Magnetization reversal in permalloy particles: Micromagnetic computations

Abstract

Magnetization distributions in a rectangular permalloy particle with an 8:1 aspect ratio are presented. When a magnetic field is applied along the easy axis of the particle, there is considerable change in the vortex pattern as the applied field varies, but the moment is nearly constant. Magnetization reversal is sudden. When a field is applied oblique to the easy axis the magnetization is rather uniform in most of the particle. When an in-plane field is applied exactly along the hard axis, a complex domain structure is formed, so that the remanence is zero, in agreement with experiment. Formation of this state requires that the applied field exceed a critical value. Upon application of an easy axis field to this complex state, the domain structure is shifted so that the magnetization increases linearly with the applied field.