Computer Simulation of the Magnetic Dipole Interaction Problem

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Abstract
Interacting systems of a large number of hysteretic bistable magnetic particles have been studied by direct calculation using digital computers. In this paper, we discuss calculations made on oriented dipole moments in a regular cubic array periodically extended parallel to the dipole axes in order to avoid demagnetization effects. Distributions of critical fields and moments are assigned to the array. The switching fields of the particles are modified by the interaction field. After the interaction fields are computed, the array is relaxed for the current applied field which may be cycled in any desired variation. The relaxation process is in order of decreasing particle vulnerability. The average interaction field has been found to be a linear function of the magnetization in agreement with the theoretical predictions of Della Torre. Distribution functions, n(Hi), have been determined. In addition a type of breakdown phenomena in these arrays suggested by Barker has been observed. In application to fine particle systems as used in magnetic recording tapes, effects such as variation in particle orientation and nonuniform dispersions may be simply introduced into a subprogram of the simulation. In a similar fashion the model can be generalized to different types of interactions and applied to other magnetic and dielectric cooperative phenomena.

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