Investigation of structural, elastic, thermal, magnetic, optical, and photocatalytic properties of nanosized Mg-Mn-Li ferrites

Abstract Nanoferrites of (Mn_1-xMg_x)_0.8Li_0.1Fe_2.1O₄ (x: 0–1.0, step 0.2) were synthesized by the sol–gel autocombustion method. The structural properties of the samples were characterized by X-ray diffraction, particle size analysis, transmission electron microscopy, and Fourier transform infrared spectroscopy. The X-ray diffraction patterns for the samples establish the nanoscale (38–54 nm) pure-phase spinel cubic structure (Fd-$$\bar{3}$$m). Also, the particle size analysis results demonstrate the narrow distribution of their particle sizes, which range from 10 to 33 nm. The impact of Mg²⁺ ion concentration on the thermal, elastic, magnetic, and optical properties of these samples was studied. The saturation magnetization decreases from 56.9 to 31.1 emu/g, and the coercivity increases from 65.8 to 106.8G with the addition of Mg²⁺ ions, showing thin S-shaped hysteresis loops revealing the samples’ soft magnetic behavior. Thermal results indicate that these samples are interesting candidates for thermoelectric applications due to their noticeably lower thermal conductivity, which ranges from 0.3572 to 0.5881 W/mK. The optical band gap values determined by using ultraviolet-visible diffuse reflectance spectroscopy range from 5.11 to 5.25 eV, where quantum confinement for crystallite size triggers a larger band gap. As the concentration of Mg²⁺ ions increases, their ability to degrade methyl green dye under ultraviolet radiation for 100 min rises from 13.6 to 61.1% with the addition of H₂O₂, an indication of their photocatalytic activity. Moreover, the optimum ferrite sample, Mn_0.4Mg_0.4Li_0.1Fe_2.1O₄, maintained its photocatalytic efficiency for at least six reaction cycles. Graphical Abstract