Investigation of Mg²⁺ Ion Substitution on the Structural, Electric, and Magnetic Properties of Soft Spinel Ferrites (NiFe₂O₄) for High-Frequency Applications

Magnesium-doped nickel ferrite nanoparticles with the chemical composition (Ni_1−xMg_xFe₂O₄, x  =  0.00, 0.20, and 0.40) have been prepared by a modified sol–gel citrate method. Structural analysis was carried out through x-ray diffractograms (XRD) and Fourier-transform infrared (FTIR) spectroscopy. The spherical-shaped morphology of the prepared nanoparticles has been confirmed by field-emission scanning electron microscopy (FESEM). The energy dispersive x-ray (EDX) analysis confirmed the presence of elements (Ni, Mg, Fe, and O) in the prepared compositions. The distribution of cations over tetrahedral and octahedral sites has been confirmed by Rietveld refinement using FullProf software. The phenomena of Maxwell–Wagner polarization is exhibited in the dielectric measurements. Cole–Cole plots showed that the net grain (R_g) and grain boundary resistance (R_gb) values are decreasing for the maximum concentration of Mg²⁺ ions in the nickel ferrites. Almost 96% deductions in the tangent loss values have been observed at high temperatures with the increasing concentration of Mg²⁺ ions in the nickel ferrites. Fitting of AC conductivity was carried out using the Jonscher Power Law function. The net magnetization saturation values also decreased from 27.7 emu/g to 16.7 emu/g upon the doping of Mg²⁺ ions in the pure nickel ferrites. These properties are all desired for materials working under high-frequency applications.