Brownian Motion of Spins

Abstract

Stochastic models of Brownian motion of a spin are discussed. If a frictional resistance is assumed to accompany the random field causing Brownian motion, the stochastic equation of spin motion leads to a Fokker-Planck equation which guarantees approach to thermal equilibrium. With a Landau-Lifshitz type friction assumed, the average magnetic moment is shown to obey the Bloch equation.