On the coercivity of cobalt-ferrite epitaxial iron oxides

Acicular γ-Fe2O3particles were treated in alkaline solution containing cobaltous and ferrous ions. When cobalt content is increased, the surface area of the oxides decreases, and cobalt-ferrite is considered to be crystallized on the surface of γ-Fe2O3. The coercivity of the oxides remarkably increases with increasing the cobalt content, and the increase of coercivity is considered to be due to the crystalline magnetic anisotropy of the cobalt-ferrite. The coercivity of the oxides is explained by considering the shape anisotropy of acicular particles and the crystalline magnetic anisotropy of cobalt-ferrite.