Structural, optical, and magnetic properties of non-stoichiometric lithium substituted magnesium ferrite nanoparticles for multifunctional applications

In the present research article, structural, optical, and magnetic properties along with Curie temperature of lithium substituted magnesium ferrite nanoparticles, Mg0.5+xLi1−2xFe2O4 (0 ≤ x ≤ 0.35) have been reported. The nanomaterial was prepared successfully using chemical-based citrate precursor sol–gel method and annealed at 550 °C. The X-ray diffraction analysis of the prepared nanomaterials confirms the formation of cubic spinel structure. The W–H plots were used to calculate crystal structure and lattice strain. The crystallite size was found to be 24 nm, 78 nm, and 50 nm, respectively, for three composition. The lattice strain was found to decrease and lattice constant was found to increase as the molar concentration of Li ion increases. The EDS measurements confirmed the presence of Mg, Fe, and oxygen. Functional group was measured using FTIR in the range of wave number 1000–400 cm−1 which confirms spinel structure. SEM are used for grain size determination with surface morphology analysis and found agglomerated nanocrystalline of different sizes. The optical properties were measured using UV/Vis/NIR and photoluminescence (PL) spectrometer. The energy bandgap was found 2.5 eV, 1.98 eV, and 2.41 eV, respectively, for the three prepared nanomaterials. While enhancement in photoluminescence spectra measured using PL spectrometer observed with decrease in lithium concentration. The magnetic properties were measured using vibrating sample magnetometer. The magnetic parameters like saturation magnetization, coercivity, and anisotropic constants were found to be increasing with the decrease in lithium ion concentration (Ms 11.63 emu/g–16.24 emu/g, Hc 110.81Oe–156.67Oe and (1342.41 to 2650.33). This non-stoichiometric structure was observed to affect the Curie temperature from 479 °C to 454 °C which often provides the possibility of this nanomaterial for broad range of applications in memory devices, isolators, circulator, etc.