Superparamagnetic Nickel Ferrite Nanoparticles Doped with Zinc by Modified Sol–gel Method

This paper reports a potential and easy method to prepare nickel ferrite nanoparticles with improved dielectric and magnetic properties by doping with zinc. The structural studies and Rietveld refinement of the XRD pattern confirm the cubic spinel structure of the ferrite phase belonging to the Fd3m space group. Morphological and elemental composition analyses of the prepared samples are carried out using scanning electron microscopy and energy dispersive spectroscopy (EDAX). The frequency variation of the dielectric constant and ac conductivity have been studied. The dependence of dielectric constant and ac conductivity on the frequency of the alternating applied electric field is explained by the Maxwell–Wagner model. The zinc doping in nickel ferrite nanoparticles is helpful in modifying the dielectric properties and thereby designing materials matching the application requirements. Magnetic measurements were carried out at 300 K and 5 K points toward an enhanced magnetic property in zinc-doped samples. The saturation magnetization value for zinc ferrite nanoparticles is around 23 emu/g at 300 K and 56 emu/g at 5 K which clearly indicates the superparamagnetic behavior of the samples. The maximum value for Ms is obtained for the Ni_0.5Zn_0.5Fe₂O₄ sample which is 74 emu/g and 101 emu/g at 300 and 5 K, respectively. The enhanced dielectric and magnetic properties inherited by Zn doping in nickel ferrite (NFO) nanoparticles suggest the improved potential of these superparamagnetic NZFO nanoparticles for various applications.