Computational Study of Magnetic Particle Alignment in External Magnetic Field Under the Influence of Viscous and Brownian Torques

Dynamics of rotational magnetic particle alignment, an inverse process to Brownian relaxation, has been studied theoretically. It was found that arbitrary viscous torque with history term due to inertia and friction of surrounding water ambient has significant effect in strong magnetic field limit. On the other hand, for weak fields it can be neglected and stochastic Brownian torque induced by random collisions of surrounding fluid molecules is dominant.

1. Introduction

Magnetic particle alignment, as Brownian rotation of the whole particle or rotation of its magnetic moment, are inverse processes to the Brownian or Néel relaxation. Their mechanism is today well known, although description of their dynamics is often simplified. In this paper we would like to address the description of dynamics of the first one—Brownian rotation of the magnetic particle during magnetic alignment.