Switching probabilities for single-domain magnetic particles

Abstract

Solving the stochastic Landau-Lifshitz equation numerically, we compute as a function of time t the probability per unit time, Ps (t), that a classical, single-domain magnetic particle with an easy uniaxial anisotropy and a collinear applied magnetic field will reverse its magnetization ("switch") via thermal activation over the energy barrier. The Ps (t) curves increase with t for small t, achieving a maximum at some time τP before decaying exponentially with time constant τD at long time, as per the standard Neel-Brown picture. Both τP and τD increase (the latter exponentially) with increasing barrier height; τP grows logarithmically with τD, consistent with a recent phenomenological "energy-ladder" model, and experiments on submicron-sized magnetic thin films. © 2005 The American Physical Society.