Diffusion After-Effect in Cobalt-Substituted Ferrites

Abstract

A Richter-type peak of magnetic loss and the disaccommodation were observed for cobalt-substituted Ni-Zn ferrites containing Fe₂O₃ less than the stoichiometric composition. These phenomena can be interpreted in terms of the diffusion of electrons between Co²⁺ ions and Co³⁺ ions. The induced anisotropy caused by the preferential occupation of Co³⁺ ions in four kinds of 16d sites may explain these phenomena. Relaxation times are represented by the equation τ=τ_∞exp (Q⁄kT), where τ_∞ are approximately 10⁻¹⁷ to 10⁻¹⁵ sec for the Richter-type peak and 10⁻¹⁰ to 10⁻¹¹ sec for the disaccommodation. Activation energies are about 0.8 to 1.0 eV for the former, and about 0.5 to 0.7 eV for the latter.