COMPUTED HYSTERESIS BEHAVIOR AND INTERACTION EFFECTS IN SPHEROIDAL PARTICLE ASSEMBLIES

The purpose of this papar is to describe a three-dimensional hysteresis model for particulate recording media. The model consists of a particle assembly with a few hundred particles and includes particle shape effects (oblate or prolate spheroids), particle anisotropy distribution, particle position/orientation variation and magnetostatic particle interactions. The total magnetization of the assembly is computed dynamically, integrating the Landau-Lifshitz-Gilbert differential equation, in combination with a self-consistent iterative approach. On one hand, lateral interactions are dominant in prolate particle assemblies and different packing fraction has a marginal influence on the interaction effects. On the other hand, axial interactions are dominant in oblate particle assemblies and different packing fraction has a substantial influence on the interaction effects. Henkel plots and delta M curves have been computed which show a positive interaction for the oblate particle assembly and a negative interaction for the prolate assembly. The coercivity and coercivity squareness increase for the oblate assembly and reduce for the prolate assembly for increased packing fraction. The oblate assembly is more resilient against perpendicular field demagnetization than the prolate assembly. The applied field angle has a substantial effect on the remanence coercivity of the oblate assembly whereas this effect is marginal in the prolate case.