Densification, magnetic and dielectric behaviour of Cu-substituted Mg–Zn ferrites

The physical, magnetic and dielectric properties of Cu-substituted Mg–Zn ferrites having the general formula of Mg0.55−xCuxZn0.45O(Fe2O3)0.97 prepared by standard double sintering ceramic technique have been studied. X-ray diffraction (XRD) patterns of the samples indicate the formation of single-phase cubic spinel structure. The lattice parameter ‘a’ is increased with increasing Cu2+ ion substitution. A significant increase in density is observed with increasing Cu content. The beneficial effect of copper ions on the densification of Mg–Zn ferrite can be reasonably explained by possible bimodal diffusion mechanism. The initial permeability μ′ shows a good stability with frequency for x = 0.0–0.25 while μ′ shows the constant value up to 200 kHz for x = 0.30 and 0.35 beyond which it falls rapidly. The permeability is found to increase as copper content increases which is consistent with the variation of density with copper ions. Saturation magnetization (Ms) increases with copper content up to x = 0.30 and then it decreases. The observed variation in Ms can be explained in terms of the cation redistribution between A and B sublattices. Dielectric constant (ɛ′) decreases with increase in frequency which is rapid at lower frequencies and slower at higher frequencies which may be due to the Maxwell-Wagner interfacial polarization. Dielectric relaxation peaks were observed for the frequency dependence of dielectric loss tangent curves. ɛ′ increases as the temperature increases which is attributed to the fact that the hoping of electrons between Fe2+ and Fe3+ ions is thermally activated on increasing the temperature.