Effect of Rare-Earth Doping on Magnetic and Electrical Transport Properties of Nanoparticle Mn-Zn Ferrite

Nanoparticles of Mn05Zn05Fe2-xLaxO4 ferrite with x = 0.05, 0.1, 0.15, 0.2 were prepared by using combustion synthesis. Formation of monophasic spinel ferrite samples were confirmed by the analysis of XRD and FTIR spectral data obtained on the samples. Particle size calculations done using Scherrer formula after applying particle strain corrections showed that the particles were in the range of 15 nm to 20 nm. Transmission electron microscopy was also employed to estimate particle size. Scanning electron microscopy was used to study the surface morphology of the samples. Magnetic measurements showed that the samples were superparamagnetic in nature. It was found that the saturation magnetization kept on reducing with increase in La concentration in the sample. The resistivity of the samples exhibited the usual semiconductor type behavior with a phonon resonance peak. The maximum resistivity of the sample was found to change between 10(2) ohm-cm to 10(8) ohm-cm that is lower by an order to 10(2) to 10(1). The dielectric constant was found to be very high with a rapid fall near Curie temperature. Thus the overall magnetic and transport properties of the samples are found to show a behavior that is different from earlier reported results. Although La replaces Fe in the material the exact reason for reduction in saturation magnetization needs to be investigated. The reduction in resistivity and enhancement in dielectric constant can be attributed to excess of electrons that are made available by La for conduction in the sample.