Structural, Optical, and Magnetic Properties of Eu3+-Substituted Ni-Mg Ferrites Synthesized via Hydrothermal Method

Eu3+ substituted nickel-magnesium ferrites with the formula Ni0.5Mg0.5EuxFe2−xO4 (x = 0.0-0.12) were successful synthesized by hydrothermal method. Herein, we investigate the effect of varying Eu3+ substitution levels on the structural, optical, and magnetic properties of the resulting ferrites. X-ray diffraction (XRD) analysis confirmed the formation of a cubic spinel structure as the dominant phase, however, at higher Eu3+ concentrations, additional diffraction peaks corresponding to a secondary hematite phase were observed, indicating a solubility limit of Eu3+ in the spinel lattice. A progressive increase in crystallite size and lattice parameter was observed with increasing Eu3+ content. Transmission electron microscopy (TEM) analysis revealed the formation of nearly spherical nanoparticles with sizes ranging 46–63 nm. Fourier-transform infrared (FTIR) spectroscopy confirmed the presence of metal-oxygen bonds in the samples through their characteristic vibrations, while diffuse reflectance spectroscopy (DRS) revealed an increase in band gap energy from 1.82 eV to 2.12 eV, suggesting structural and electronic modifications at higher Eu3+ substitution levels. All samples showed ferromagnetic behaviour, as measured by vibrating sample magnetometry (VSM); however, saturation magnetization, coercivity, and remanence decreased with increasing Eu3+ content. These results highlight the potential of Eu-substituted Ni-Mg ferrites for applications in magneto-optical devices, high-frequency electronics, and spintronic technologies.