MONTE-CARLO CALCULATIONS OF THE MICROSTRUCTURE OF BARIUM FERRITE DISPERSIONS

A Monte Carlo (MC) model has been developed to investigate the influen ces of the volume packing fraction and applied field on the equilibriu m microstructure of a dispersion of barium ferrite particles. We accou nted for magnetostatic interaction effects by using a surface charge m odel which allows the calculation of the energy term required for the Metropolis-type MC algorithm. In addition to single particle moves, th e model employs a clustering algorithm, based on particle proximity, i n order to take into account the cooperative behaviour of the particle s bound by magnetostatic energy. The stacks which are thought to be ch aracteristic of barium ferrite systems are an example of this type of binding. Our study provides strong evidence, in agreement with experim ent, for the formation of stacks both in the zero field and in the app lied field equilibrium configurations. The simulation also predicts, b y considering the effects of the packing density, that the dispersion properties are strongly affected by the mobility of these stacks. The equilibrium particle configurations have been investigated using a cor relation function and visualized by computer graphics. The magnetic be haviour has been investigated by calculation of the magnetization curv e.