Engineering MgFe₂O₄ nanoparticles to enhance magnetic, optical, and dielectric performance

This research investigated the effects of solution pH during synthesis and annealing on the structural, magnetic, optical, and dielectric properties of MgFe2O4 synthesised using the citric acid-assisted sol-gel auto-combustion method. Structural data showed that crystallinity, lattice parameters, and cation distribution were strongly influenced by both pH and annealing temperature. Optimal morphology and crystallinity were achieved at pH 7 and an annealing temperature of 550 °C for 3 h, under which cation ordering and defect reduction were effectively achieved. Magnetic characterisation revealed a significant improvement in saturation magnetisation (20.6 emu/g) under optimal conditions, attributed to increased super-exchange interactions. The optical bandgap was modulated by more than 11% (2.04 to 2.30 eV) by adjusting pH-mediated surface chemistry and subsequent defect states. The sample synthesised at pH 9 exhibited the highest values of ε’, ε”, and σac. These results conclusively demonstrate that accurate control of synthesis pH and annealing enables the design of multifunctional properties in MgFe2O4 nanoparticles, providing a solid foundation for their application in high-end magnetic, optical, and electronic devices.