ROTATIONAL DIFFUSION OF A TRACER COLLOID PARTICLE .3. WEAK EXTERNAL-FIELD EFFECTS

We study the orientational time correlation functions of a tracer colloid particle which carries a magnetic moment in the presence of a weak external magnetic field. The tracer interacts with other particles in a low density suspension through hard sphere pair potentials and hydrodynamic forces. We show that at intemediate times the approximation for the correlation functions, introduced in the previous paper in this series, is a good one. Using a perturbative technique and angular momentum recoupling theory, we evaluate to second order the effect of an external magnetic field on the relaxation of correlations. We present numerical results for the correlations at various suspension densities and field strengths. © 1990.