Investigation of structural, electrical, and magnetic anisotropy studies of the rare earth (Tb3+) ion substituted Mg-Ni nanocrystalline ferrites for spintronic applications

Tb³⁺ ion-doped Mg-Ni nanocrystalline ferrites with the chemical formula Mg_0.2Ni_0.8Tb_xFe_2-xO₄ (x = 0.00 to 0.25) were synthesized using the sol-gel auto-combustion method. The structural properties of all samples were analyzed using X-ray diffraction, FTIR, and UV–visible spectroscopy. XRD studies confirmed the existence of a secondary phase in samples with x = 0.15 to higher concentrations. The lattice constant decreased, and the X-ray density increased with increasing Tb³⁺ ions. The two prominent absorption bands observed in the FTIR spectra confirmed the spinel structure. The direct band gap obtained from the UV–vis investigation was in the range of 1.85–1.67 eV, confirming semiconducting behavior. The grain size calculated using FESEM increased with increasing Tb³⁺ concentration. DC electrical conductivity measurements also indicated the semiconducting characteristics of the samples. Magnetic measurements were performed using VSM. The addition of Tb³⁺ ions resulted in a decrease in the saturation magnetization from 29.32 (x = 0.00) to 8.61 (x = 0.25) emu/g. In addition, the anisotropy constant and anisotropy field decreased with increasing Tb³⁺ ion content because of secondary phase formation. Tunable magnetic softening, semiconducting nature, and anisotropy control are essential for tailoring materials for spintronic applications.