Optical and Magnetic Properties of Mg-Doped Cobalt Ferrite (Co1−xMgxFe2O4) Nanoparticles

Background: Mg-doped cobalt ferrite (Co1−xMgxFe2O4, x = 0, 0.2, 0.4, 0.6, and 0.8) nanoparticles were investigated to evaluate the influence of Mg2+ substitution on the structural, optical, and magnetic properties of cobalt ferrites. Methods: Co1−xMgxFe2O4 nanoparticles were synthesized using the sol–gel autocombustion method and characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, and vibrating sample magnetometry. Results: Mg doping preserved the cubic spinel structure but caused redistribution of Fe3+ ions between tetrahedral and octahedral sites, resulting in a slight change in the lattice constant. The X-ray density decreased from 5.68 to 4.83 g/cm3 as x increased from 0 to 0.8, while the optical bandgap increased from 1.75 to 2.3 eV. Fourier transform infrared spectra exhibited two characteristic absorption bands (400–600 cm–1) corresponding to tetrahedral- and octahedral-site metal–oxygen bonds. Mg2+ substitution altered the distribution of Mg2+ and Fe3+ ions among crystallographic sites and consequently modified the magnetic properties. Conclusions: Mg2+ doping effectively modified the structural, optical, and magnetic properties of CoFe2O4 nanoparticles while preserving the spinel structure. These findings demonstrate that Mg substitution provides an effective approach for tailoring the functional properties of cobalt ferrites for optoelectronic and magnetic applications.