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

Tb 3+ ion-doped Mg-Ni nanocrystalline ferrites with the chemical formula Mg 0.2 Ni 0.8 Tb x Fe 2-x O 4 (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 Tb 3+ 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 Tb 3+ concentration. DC electrical conductivity measurements also indicated the semiconducting characteristics of the samples. Magnetic measurements were performed using VSM. The addition of Tb 3+ 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 Tb 3+ ion content because of secondary phase formation. Tunable magnetic softening, semiconducting nature, and anisotropy control are essential for tailoring materials for spintronic applications. • Tb 3+ ion-doped Mg-Ni nanocrystalline ferrites with the formula Mg 0.2 Ni 0.8 Tb x Fe 2-x O 4 (x = 0.00–0.25) were synthesized using the sol-gel auto-combustion method. • XRD studies showed that samples up to x = 0.10 had a cubic structure, while the x = 0.15–0.25 samples exhibited an orthorhombic phase. • FESEM studies showed particle sizes of 65–102 nm, with systematic growth upon doping. The EDAX analysis revealed the sample composition and purity. • Direct band gap energy studies from the UV spectra obtained were 1.85–1.67 eV, and temperature variation electrical conductivity measurements confirmed the semiconducting nature. • Magnetization studies revealed softer magnetic behavior with the addition of Tb 3+ ions, indicating its suitability for high-frequency spintronic and sensing applications.