Effect of Mn2+ substitution on structural, electrical transport and dielectric properties of Mg-Zn ferrites

Here we have investigated the effect of Mn2+ substitution on the structural, electrical transport and dielectric properties of Mg-Zn ferrite having chemical formula MnxMg0.5−xZn0.5Fe2O4 (0.00≤x≤0.30) synthesized by an oxalate precursor chemical method. X-ray diffraction study reveals the formation of single cubic structure with spinel lattice symmetry without secondary phases having the crystallite size in the range from ~ 25.35−30.36 nm. The Mn2+ substitution leads to the expansion of spinel lattice unit cell of Mg-Zn ferrite system as evidenced from the increase of lattice constant (a) with respect to Mn2+ content. Decrease in the d.c. electrical resistivity as a function of temperature confirms the semiconducting nature of the Mn2+ substituted Mg-Zn ferrite; which is attributed to the Verwey hopping mechanism between Fe2+⇔ Fe3+ ions and Mn2+⇔ Mn3+. The frequency (100 Hz−1 MHz) dependence dielectric properties viz. dielectric constant and dielectric loss measurement shows the usual dielectric dispersion in accordance with the Maxwell-Wagner type interfacial polarization. The a.c. resistivity measurement (100 Hz−1 MHz) suggests the small polaron hopping type conduction is present in the Mn2+ substituted Mg-Zn ferrite system.