Composition and Annealing Process Influence on Structure, Local Structure, Electrical, and Magnetic Properties of MnFe₂O₄

Manganese ferrite (MnFe2O4) nanoparticles were effectively synthesized through mechanical milling, and the influence of Mn2O3:Fe2O3 composition, along with annealing temperatures of 500 and 600 °C, was systematically investigated. X-ray diffraction (XRD) analysis confirmed a cubic symmetry for the structure, while Raman spectroscopy elucidated the presence of tetrahedral and octahedral coordination with A1g, Eg, and T2g vibrational modes. An increase in Fe2O3 content in the sample designated MF12 led to the emergence of additional Fe2O3 phases. Fourier transform infrared (FTIR) spectroscopy highlighted that annealing significantly impacted the cation distribution and bonding characteristics, exhibiting distinct behaviors between the MF11 and MF12 compositions. X-ray absorption near-edge structure (XANES) analysis indicated mixed Fe3+/Fe4+ oxidation states, which have implications for the magnetic properties of the material. Extended X-ray absorption fine structure (EXAFS) measurements revealed local structural distortions influenced by the synthesis conditions. Notably, annealing at 500 °C improved direct current (DC) conductivity by enhancing crystallinity and facilitating electron hopping, while annealing at 600 °C resulted in decreased conductivity due to the disruption of the spinel structure and formation of Fe2O3. Additionally, the dielectric properties were examined, finding that space charge polarization and Maxwell–Wagner effects played pivotal roles, with significant dielectric loss and relaxation peaks observed in the MF11_500 sample. It was also noted that magnetization values were diminished with higher Fe2O3 content, a trend attributed to the formation of secondary phases. These findings underscore the importance of composition and annealing parameters in modulating the structural, electrical, and magnetic properties of MnFe2O4 nanoparticles.