Influence of Gd doping on the structural, magnetic, photocatalytic, antibacterial, ESR and Mössbauer spectroscopy studies of NiMg nano ferrite

NiMg_0.5Gd_xFe_1.5-xO₄ ferrite (x = 0.0, 0.05 and 0.1) with crystallite sizes ranging from 17.70 to 28.38 nm were synthesized using the sol–gel auto combustion method. The X-ray diffraction (XRD) results confirmed the formation of a cubic spinel phase. Magnetization measurements revealed paramagnetic properties a decrease in saturation magnetization from 9.96 to 3.26 emu/g with increasing Gd content, while coercivity was fluctuating between 138.3 and 166.4 Oe. ESR spectra showed variations in signal intensity and resonance field with doping, correlating with the observed magnetic changes. Mössbauer spectroscopy analysis supported the redistribution of Fe³⁺ ions between A and B sites, which directly impacted hyperfine magnetic interactions and, consequently, the functional properties. Photocatalytic studies demonstrated that the NiMg_0.5Gd_0.05Fe_1.45O₄ sample exhibited the highest degradation efficiency of MG dye (90.7 %) under sunlight. Antibacterial activity tests revealed negligible inhibition for the undoped sample, whereas Gd doping (x = 0.05) significantly enhanced antibacterial efficiency, particularly against B. subtilis and E. coli, consistent with the improved magnetic and surface-active characteristics. Overall, the correlation among magnetic, and catalytic characterizations demonstrates that Gd doping tailors the multifunctional behaviour of Ni–Mg ferrites, making them promising candidates for environmental and biomedical applications.