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-MgFe 2 O 4 produced via sol-gel-auto-ignition. XRD(X-ray-diffraction) confirms nano-crystalline-spinelphase 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,Bsites, 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 dielectricconstant (ε′,ε″),losses, while AC-conductivity(σ ac ) increases notably, follows power-law behavior. Impedanceanalysis clearly show grain-boundaries govern dielectric-response at high frequencies. The Nyquist plot analysis reveals fitted equivalent-circuit parameters (grain resistance R g and grain-boundary resistance R gb ) 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.