Synthesis and investigation of structural, morphological, magnetic, dielectric and impedance spectroscopic characteristics of Ni-Zn ferrite nanoparticles

A series of ferrite samples with general formula Ni1-xZnxFe2O4 (x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) synthesized using sol-gel self-assisted combustion method have been investigated. X-ray diffraction patterns confirmed the spinel cubic structure of all the samples with Fd3m space group. Lattice constant, crystallite size, bulk density, and X-ray density increase while porosity of the samples decreases with increasing Zn contents. Rietveld's refinement was also carried out to compare the calculated and observed X-ray diffraction patterns, which subsequently confirmed the evaluated structural parameters. Irregular shaped grains were mainly decreasing in size in the series of samples, revealed by images obtained using field emission scanning electron microscope. A decrease in saturation magnetization was observed with Zn substitution at Ni-site while coercivity was increased, exhibiting a transition towards hard ferromagnetic behavior. An increase in remanent magnetization was also evident, mainly attributed to an increase in magneto-crystalline anisotropy energy. A systematic investigation of frequency dependent electrical and dielectric properties has also been performed. Incorporation of Zn at Ni-site resulted in increase in ac conductivity while resistance and reactance of the samples were decreased. Nyquist and modulus graphs were plotted and their characteristic behaviors were analyzed.