Interaction and dimensional effects in micromagnetic models

In this article the effects of dipolar and exchange interactions on the remanence ratio and coercivity in granular solids are examined using a generalized three-dimensional Monte Carlo model. This model allows the final configuration of magnetic moments to be calculated as a function of concentration, temperature and magnetic field. The results show that for a system of polydispersed grains having their anisotropy axes oriented at random, both the remanence ratio and coercivity increase with increasing exchange interaction. In addition the magnetization loops exhibit regions where the reversal slows down and gives rise to distinct quasi-bimodal behavior. These effects are due to the fact that the exchange interactions are not uniform throughout the system. This model can account for many features observed in a wide range of real materials. (C) 1997 American Institute of Physics.