Dependence of the magnetization relaxation time of single-domain ferromagnetic particles on damping in the brown model

Analytical expressions for the magnetization relaxation time tau of sin-le-domain ferromagnetic particles with cubic or uniaxial anisotropy in a static transverse magnetic field are derived. The derivation is based on calculating the escape rate of a Brownian particle from a potential well; this technique is applicable at any damping and is generalized to the case of magnetic relaxation of superparamagnetic particles. The validity of the expressions obtained for tau is checked against a numerical solution of the Landau-Lifshitz-Gilbert equation over the whole range of damping (very low, intermediate, and high damping and the crossover region between L low and intermediate damping). (C) 2005 Pleiades Publishing, Inc.