The effect of annealing on the structure of cobalt modified iron oxide particles. Part II

A new high coercivity cobalt modified iron oxide particle series has been prepared by annealing in a nitrogen atmosphere. The dependence of coercivity (Hc), Hc-aging, temperature dependence of Hc, and magnetic tape properties have been studied as a function of annealing temperature. X-ray photoelectron spectroscopy (XPS) has been used to correlate the changes in magnetic properties to the cobalt concentration gradient near the particle surface. As in Part I of the study, most of the changes observed are consistent with diffusion of cobalt from the surface into the particle core.