Anisotropy field distributions in magnetic recording particles

First-quadrant moment versus field data for several types of recording media based on γ-Fe2O3 are least-squares fit to anisotropy field distributions within the Stoner–Wohlfarth model. For γ-Fe2O3, the mean anisotropy field is less than expected from the nominal axial ratios of the particles. All media show broad distributions in anisotropy fields, especially those containing Fe2+. Coercivities calculated assuming coherent rotation in γ-Fe2O3 are much smaller than predicted from the nominal axial ratios, but larger than experimental. Predicted coercivities for the other samples are relatively closer to experimental, reflecting broader anisotropy field distribution widths relative to the mean values.