Optimizing functional properties of Mg-nanoferrite by varying thermal annealing time

This study explores influence of duration of thermal-treatment for tuning structural,magnetic,dielectric response of nano-MgFe2O4 produced via sol-gel-auto-ignition. XRD(X-ray-diffraction) confirms nano-crystalline-spinel-phase growth, grain sizes ranging from 25.3 to 49.3 nm following annealing at 500 °C for 1–3 h. Structural analysis reveals a non-monotonic variation in lattice parameter, and progressive grain growth. Magnetic characterization indicates enhanced A-A, A-B super-exchange-interaction, weakened B-B exchange, leading to decreased Néel magnetic moment. Cation redistribution shows, increased Mg²⁺ and reduced Fe³ ⁺ at the B-site, altering the oxygen positional parameter and inversion degree. EDS validates that Fe,Mg,O are present in the studied samples. SEM images confirm particle-aggregation, irregular size- dispersal of particles, owing to samples’ magnetic-nature. Mössbauer spectroscopy reveals two magnetic-sextets corresponding to Fe³ ⁺-ions at A,B-sites, with isomer shift values confirming the +3 oxidation state. A non-magnetic doublet (~23%) is attributed to a spin-disordered shell region. Frequency-dependent-dielectric-measurements show decreasing dielectric-constant (ε′,ε″),losses, while AC-conductivity(σac) increases notably, follows power-law behavior. Impedance- analysis clearly show grain-boundaries govern dielectric-response at high frequencies. The Nyquist plot analysis reveals fitted equivalent-circuit parameters (grain resistance Rg and grain-boundary resistance Rgb) that decrease progressively with annealing time, confirming improved charge transport across grain boundaries. The thermal annealing time–controlled evolution of structural,magnetic,dielectric properties indicates the suitability of Mg nanoferrites for microwave-device-applications.