Effect of interaction on magnetic properties of a particulate medium

Samples of magnetic particles were prepared in dry powder form, as well as in a plastic binder system. Magnetic measurements were made on the samples as function of the volumetric packing factor. Coercive force Hc, squareness, and anhysteretic magnetization measurements are correlated with the uniformity of particle dispersion. It was found that the behavior of Hc, squareness, and the initial anhysteretic susceptibility as a function of the packing factor are good indications of the degree of dispersion of the particles. It is shown that if the particles are well dispersed, Hcincreased with increased dilution, and the initial anhysteretic susceptibility increased at both high and low dilutions. A mathematical model is developed to explain the observed results. The model consists of a double distribution of interaction fields to account for the well-dispersed and the agglomerated particles.