Effect of Mg substitution on the magnetic properties of Ni–Zn ferrites

Abstract

Nickel–zinc ferrites with the general chemical formula, $\hbox {Ni}_{0.3}\hbox {Zn}_{0.7-x}\hbox {Mg}_{x}\hbox {Fe}_{2}\hbox {O}_{4}$ with x varying from 0.00 to 0.25 in steps of 0.05, have been prepared by conventional solid-state method. Final sintering of the samples was carried out at $1200{^{\circ }}\hbox {C}$ for 6 h in air to investigate their structural and magnetic properties. X-ray diffraction patterns of all the samples confirm the cubic spinel structure. Percent porosity and lattice constants of the samples are similar for all the samples except for the sample with $x=0.05$ implying that the changes in magnetic properties could be solely attributed to the effects caused by substitutions only. The saturation magnetization has been observed to increase continuously with the substitution of $\hbox {Mg}^{2+}$ ions in the place of $\hbox {Zn}^{2+}$ ions. Curie temperature of the system was also found to increase from $261{^{\circ }}\hbox {C}$ ($x=0.00$) to $364{^{\circ }}\hbox {C}$ ($x=0.25$) with the increase in magnesium content. Smooth coercivity variation suggests better structural homogeneity. The results are discussed in the light of the distribution of the cations among octahedral and tetrahedral sites.