Magnesium-Zinc ferrite substituted with rare earth ion Gd3+ with y = 0.05 and 0.10 are investigated. X-ray diffraction, IR absorption study of these compositions revealed the formation of single phase spinels. The temperature dependence of Thermo-electric power (TEP) is measured and then mobility of each sample calculated. The values of TEP (α) show n type conductivity suggesting the mechanism of conduction to be predominantly by electron hoping. On substitution of Gd3+ ion, TEP decreases which is assigned to the decrease of population of Fe3+ ions at the octahedral B site.
