Effect of surface properties on cobalt modification of iron oxides

Nine different gamma Fe/sub 2/O/sub 3/ samples were surface-modified with Fe/sup 2+/ and Co/sup 2+/ ions. The coercivity (H/sub c/), the specific surface area (SSA), and the acid-base characteristics of the core particles were measured, as well as the coercivity of the final product. A relationship was found between the integral surface charge density of the core particles and the surface efficiency, defined as the difference between the final and the initial H/sub c/ normalized by the SSA at a constant amount of Fe/sup 2+/ and Co/sup 2+/. The technological importance of this finding is that the efficiency of the cobalt doping process can be related to measurable surface properties of the core particles.<>