Quasi-two-dimensional Brownian dynamics simulations of the regime change in the aggregate structures of cubic haematite particles in a rotating magnetic field

Abstract

In the present study, by means of quasi-two-dimensional Brownian dynamics simulations, we have addressed the physical phenomena of a suspension composed of cubic haematite particles in a rotating magnetic field in order to elucidate the relationship between aggregate structures and their response to a rotating magnetic field. In the case of a relatively weak magnetic particle-particle interaction, single particles remain without aggregating to form specific clusters, and the magnetic moment of single particles tends to follow a change in the direction of the rotating magnetic field. In the case of a strong magnetic particle-particle interaction, closely-packed clusters with a face-to-face configuration tend to form in the system, although the individual magnetic moments of the constituent particles do not follow the change in the magnetic field direction. As the magnetic field strength is increased, closely-packed structures are transformed into aggregate structures with an offset face-to-face configuration. In this situation, the magnetic moments of constituent particles are strongly restricted to the magnetic field direction, and the aggregates themselves may significantly rotate to follow the change in the orientation of the rotating magnetic field.