International Journal of Science and Technology (IJST)

Composition-Controlled Structural, Optical, Photoluminescence and Magnetic Properties of NiₓMn₁₋ₓFe₂O₄ Nanoparticles Synthesized by Co-precipitation

A composition series of NiₓMn₁₋ₓFe₂O₄ nanoparticles (x = 0, 0.3, 0.5, 0.7 and 1.0) was investigated to establish how Ni²⁺ substitution modifies the coupled structural, optical and magnetic behavior of manganese ferrite. The samples were prepared by co-precipitation followed by thermal treatment, and the resulting powders were examined by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), UV-Visible spectroscopy, photoluminescence (PL) spectroscopy and vibrating sample magnetometry (VSM). XRD confirms a cubic spinel ferrite framework for all compositions, with a lattice parameter decreasing from 8.3317 Å for x = 0 to 8.3137 Å for x = 1.0, indicating lattice contraction in the Ni-rich end member. FTIR supports ferrite formation through the tetrahedral metal-oxygen vibration, which shifts from 513 to 554 cm⁻¹ with increasing Ni content. SEM reveals agglomerated quasi-spherical nanoscale domains, while EDX verifies progressive replacement of Mn by Ni and cation-normalized formulas close to AB₂O₄ stoichiometry. UV-Visible Tauc analysis gives a non-monotonic direct optical band gap, increasing to 2.200 eV at x = 0.3 and then decreasing to 1.823 eV for x = 1.0. PL spectra show near-UV/violet emission around 378-382.5 nm and weaker defect-related visible emission, indicating surface and vacancy-associated recombination. VSM results show ferrimagnetic hysteresis, with the apparent high-field moment increasing toward the Ni-rich composition. The integrated results demonstrate that Ni substitution is an effective route for tailoring multifunctional spinel ferrites for optoelectronic, magnetic, sensing and photocatalytic applications.