The Magnetic Anisotropy Induced by Electron Diffusion in Co_1+2xFe_2−2xO₄ and Fe_1−2xNi_2xCo₂O₄

Abstract

A detailed study of the magnetic anisotropy of a Co_1.1Fe_1.9O₄ single crystal at 77°K revealed that, after cooling in a magnetic field, a relatively small uniaxial anisotropy is superposed on the large cubic anisotropy (K₁ and K₂). Rotational hysteresis is present at 77°K which is explained in terms of the irreversible wall displacement and the relaxing anisotropy energy. The presence of large rotational hysteresis in polycrystalline specimens CoFe₂O₄∼Co₃O₄ is also shown and is explained on this basis. Preliminary data on the relaxation time of the phenomenon are presented. All the data are consistent with the mechanism presented by Mizushima, which assumes the electron diffusion between Co²⁺ and Co³⁺ions. Data in the series Fe_1−2xNi_2xCo₂O₄ are also presented. Suggestions are made that the rotational hystereses observed in Co₂Ba₂Fe₁₂O₂₂ and BaCo_δTi_δFe_12−2δO₁₈ at low temperatures are caused by the same mechanism.