MAGNETIZATION SWITCHING IN SINGLE-DOMAIN FERROMAGNETS

A model for single-domain uniaxial ferromagnetic particles with high a nisotropy, the Ising model, is studied. Recent experimental observatio ns have been made of the probability that the magnetization has not sw itched, P-NOT. Here an approach is described in which it is emphasized that a ferromagnetic particle in an unfavorable field is, in fact, a metastable system, and the switching is accomplished through the nucle ation and subsequent growth of localized droplets. Nucleation theory i s applied to finite systems to determine the coercivity as a function of particle size and to calculate P-NOT. Both of these quantities are modified by different boundary conditions, magnetostatic interactions, and quenched disorder. (C) 1998 Elsevier Science B.V. All rights rese rved.