Structural, magnetic and electrical properties of nanocrystalline zinc ferrite

Nanoparticles of ZnFe2O4 with grain size of 30nm have been synthesized via sol-gel auto combustion method and characterized using DSC (differential scanning calorimetry), XRD (X-ray diffraction), SEM (scanning electron microscopy), EDAX (energy dispersive X-ray analysis), FTIR (Fourier transform infrared spectroscopy), VSM (vibrating sample magnetometer) and Ac-electrical conductivity measurement setup. Structural analysis using XRD and FTIR show the formation of spinel structure in nano ZnFe2O4 particles. The cation distribution in the sample has been estimated theoretically and the results show that as-prepared nanoparticles of ZnFe2O4 have partially inverted ionic distribution in comparison with that of bulk zinc ferrite. Results from EDAX indicate the ratio of Fe:Zn as close to 2:1. The presence of a weak ferrimagnetic phase for nano ZnFe2O4 at room temperature has been established from its hysteresis behavior. Redistribution of cations occurring at nano-regime and surface spin canting of nanoparticles of ZnFe2O4 are expected to be responsible for the presence of magnetic ordering in nano ZnFe2O4. The Curie temperature of nano ZnFe2O4 determined from magnetization versus temperature measurement is equal to 375 degrees C. The electrical conductivity of the present ZnFe2O4 at a frequency of 100 kHz at room temperature is observed to be 2.11 x 10(-8) Omega(-1) cm(-1) which is four orders lesser in magnitude than the value of bulk ZnFe2O4. Overall conductivity response with respect to temperature and frequency confirm that ZnFe2O4 tends to become more dielectric in the nano-regime. (C) 2011 Elsevier B. V. All rights reserved.