Synergistic effect of heat treatment on structural, magnetic and dielectric properties of spinel ferrite nanoparticles

Polycrystalline Ni1-xCoxFe2O4 ferrite nanoparticles (NPs) have been prepared by evaporation method in the presence of egg white as a bio-template. In this paper, the results of microstructure, magnetic and dielectric behavior of heat treated Ni0.8Co0.2Fe2O4 at 600 degrees C, 750 degrees C and 900 degrees C are reported. The single phase cubic structure without the traces of secondary phases was confirmed by XRD. Sintering process promotes the rate of the crystallization process and the crystallite sizes were found to be in the range of 10-22nm. TEM micrograph revealed the shape of ferrite particles to be nearly spherical. The averageparticle size estimated from TEM is well matched with the crystallite size estimated from XRD. The nature of magnetization curves indicates the influence of core-shell interactions on the magnetic properties of the present ferrite system. The cation distribution estimated from XRD results excellently supports the structural behaviour. The observed increase in Co2+ ion concentration at B-site has to increase the magnetocrystalline anisotropy leading to increase in the coercivity, but opposite phenomenon was observed. A maximum value of 48emu/g was reported for saturation magnetization. The variation of particle size played a major role in dielectric and magnetic properties. The results are interpreted in terms of cation distribution and magnetocrystalline anisotropy presuming the possible core-shell interactions.