, Volume 60, Issue 3-4, pp 473-484

First-passage-time approach to overbarrier relaxation of magnetization

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Abstract

We consider the irreversible dynamics of the magnetization vectorM in a single-domain particle. The dynamics is given by a stochastic phenomenological equation due to Gilbert. It contains a damping field proportional toM and a corresponding white noise field component. The probability distribution function satisfies a Fokker-Planck equation derived by Brown. We give the overbarrier decay rateκ out of a metastable minimum. First we rederive the well-known expression forκ for an axially symmetric model. We argue that this result is unphysical. For systems of general point symmetry of the magnetic anisotropy energy we giveκ in both the low-damping and intermediate- to high-damping limits.