Rotational motion and rheology of solid bodies in magnetic fluids

M. C. Miguel - D. Reguera - J. M. Rubí

Departament de Física Fonamental, Facultat de Física, Universitat de Barcelona, Av. Diagonal 647, 08028 Barcelona, Spain

Abstract
We discuss the complex rotational dynamics of a suspension of nonmagnetic solid bodies ({\em magnetic holes}) in a ferrofluid phase. Each one of these particles bears an induced magnetic moment equal to the magnetic moment of the ferrofluid volume they displace. The rotational dynamics of these particles is strongly affected by a rotating magnetic field. As a result, we find that a single hole rotates just in the opposite direction of that of the field. At higher concentrations of holes, dipolar interactions between the holes magnetic moments induce aggregation. We study the anomalous rheology of a suspension of tightly bounded dimers, resulting from their peculiar dynamics, when driven by the external field and a shear flow. Figs 3, Refs 16.