Langevin equation for the rotation of a magnetic particle

Abstract

Abstract We investigate Brownian motion on a curved surface with the help of the covariant Langevin and Fokker–Planck equations. As a special example we address the orientational diffusion of a ferromagnetic particle immersed in a viscous fluid under the influence of a time‐dependent magnetic field. This system may model the recently discovered thermal ratchet behaviour in ferrofluids. Numerical simulations of the Langevin equation are shown to be in good agreement with results from the solution of the Fokker–Planck equation reported previously. Copyright © 2004 John Wiley & Sons, Ltd.