Magnetization reversals in elliptical permalloy particles

We use the micromagnetic simulation to study the reversible and irreversible magnetization processes of the single-domain elliptical permalloy particles. The magnetization curve of the reversible process, which has no hysteresis, obtained by applying the field along the hard axis of the elliptical particle is almost linear, as is the case in the single-domain ellipsoidal particle. On the other hand, due to the occurrence of the nonuniform reversal, the switching field of the irreversible process, which has hysteresis, is reduced significantly compared to that predicted by the Stoner-Wohlfarth model. The nucleation fields of elliptical particles are calculated as a function of ellipse's aspect ratio, and the function reveals a step-like behavior.