Stress effects on complex permeability spectra of Mn-substituted cobalt ferrite

Abstract

The effects of axial applied stresses on the magnetization processes in Mn-substituted cobalt ferrite (CoMnxFe2-xO4 with x = 0 to 0.4) toroids have been studied by measuring the circumferential complex permeability spectra μ* = μ′ − iμ″ from 1 kHz to 15 MHz. The μ* spectra were described using a dispersion equation to determine the relative susceptibilities due to domain wall motion (χD0) and magnetization rotation (χS0). Mn-substitution into cobalt ferrite was found to reduce the magnetocrystalline anisotropy and hence the susceptibility is increased. Under axial compressive stresses, χD0 and χS0 of all samples decrease. The Mn-substituted samples with x = 0.2 and 0.3 show larger reductions in χD0 and χS0 than the pure cobalt ferrite. The stress effects on χS0 and the dependence of the magnetomechanical effect on Mn content were reproduced in model calculations by taking into account the combined effects of stress-induced and magnetocrystalline anisotropies on magnetization rotation.