Interaction forces between soft magnetic particles in uniform and non-uniform magnetic fields

Abstract

The influence of the magnetization of a soft magnetic sphere on the surrounding magnetic field is measured and characterized. The interaction force between two soft magnetic particles is directly measured using an ultra precision load sensor in uniform and non-uniform magnetic fields. The interaction force largely follows an inverse fourth power law as a function of separation distance between particle centers. At small distances, the effect of magnetization of one particle on the magnetization of its adjacent particle causes the attractive (repulsive) force to be larger (smaller) than that predicted by the inverse fourth power law. The theoretical prediction based on a modified dipole model, that takes into account the coupling effect of the magnetization among soft magnetic particles, gives excellent agreement with the measured force in a uniform magnetic field. The interaction force under a non-uniform applied magnetic field can be reasonably predicted using the dipole–dipole interaction model when the local magnetic field is used to determine the magnetization.