Recent progress in the interpretation of nucleation fields of hard magnetic particles

Abstract In permanent magnets based on rare earth-transition metal compounds the value of the coercive field, H c , as well as the angular dependence of H c deviates considerably from the predictions of the conventional Stoner-Wohlfarth theory. This discrepancy in general is attributed to the role of microstructure in sintered and rapidly quenched magnets. In this paper we have studied the process of magnetization reversal in small parallelepipeds taking into account the effect of a strong inhomogeneous demagnetization field, H d , at the edges, and of oblique applied fields. On the basis of micromagnetism it is shown that the nucleation field; H N , is reduced considerably by the demagnetization field at edges and that the angular dependence of H C is less pronounced than in the case of ellipsoidal particles.