Interparticle interactions and the switching field distribution of barium ferrite media

A series of barium ferrite disks with a variation in volumetric packing density from 1.5% to 35% were investigated to determine the effect of interparticle interactions on the switching field distribution (SFD) of the media. Kelly et al. (1989) introduced a parameter ΔM(H) to highlight deviations from the theoretical non-interacting assembly. The degree of interparticle interactions were determined from the principal remanence curves and the subsequent calculation of the ΔM(H) parameter. It was found that the SFD of these disks became narrower as the volumetric packing density increased, and that the SFD width strongly correlated with the strength of the interparticle interactions as measured from the ΔM(H) plot. Examination of scanning electron micrographs of these disks revealed that for the low-packing-density disks, separation between the stacks of particles was large and that the separation decreased as the volumetric packing density was increased. It is believed that the properties of the media result not only from the large interparticle interaction arising from particle stacking, but also from the interaction between the stacks