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Abstract
The effect of interactions on the properties of granular magnetic materials is numerically modeled as a function of temperature and applied field. A three-dimensional random geometry is utilized, and the grains are given the properties of bulk hexagonal Co. The effects of magnetostatic and exchange interactions are considered in the calculation of M-H loops and DC field-cooled magnetization curves. The effect of exchange is introduced by allowing the grains to cluster. The M-H loop calculations are carried out using quasi-static energy minimization. It is found that magnetostatic and exchange effects lower both the coercivity and remanence of the material. The thermal calculations are carried out using either the Metropolis algorithm or variable time step Monte-Carlo methods. It is found that the blocking temperature of the grains is not significantly affected by the presence of magnetostatic interactions. The clustering of grains, however, leads to a net thermal stabilizing effect in the material.
