Magnetic, magnetostrictive, and AC impedance properties of manganese substituted cobalt ferrites

In this study, we investigated the effects of substituting Mn3+ for some Fe3+ in spinel lattice on the structure, magnetic properties, magnetostriction behavior, and AC impedance characteristics of cobalt ferrites. The manganese substituted cobalt ferrites (Co-Mn ferrites), CoMnxFe2-xO4, with x varied from 0 to 0.3 in 0.1 increments, were prepared by solid-state reaction. XRD examination confirmed that all sintered Co-based ferrites had a single-phase spinel structure. The average grain size, obtained from SEM micrographs, increased from 8.2 mu m to 12.5 mu m as the Mn content (x) increased from 0 to 0.3. Both the Curie temperature and coercivity of Co-based ferrites decreased with greater amounts of Mn, while the maximum magnetization (at H=6 kOe) of Mn-substituted cobalt ferrites was larger than that of the pure Co-ferrite. Magnetostrietive properties revealed that the pure Co-ferrite had the largest saturation magnetostriction (lambda(s)), about -167 ppm, and the CoMn0.2Fe1.8O4 sample exhibited the highest strain sensitivity (Id lambda(perpendicular to)/dHl(m)) of 2.23 x 10(-9) A(-1)m among all as-prepared Co-based ferrites. In addition, AC impedance spectra analysis revealed that the real part (Z') of the complex impedance of Co-Mn ferrites was lower than that of pure Co-ferrite in the low frequency region, and the Co-based ferrites exhibited semiconductor-like behavior. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.