Effect of Ag substitution on magnetic and dielectric properties of Mn_0.5Zn_0.5Fe₂O₄ nanospinel ferrites: Mossbauer study

The controlled substitution of Ag into Mn–Zn spinel ferrites offer a promising strategy to tailor their magnetic and dielectric properties for advanced functional devices. In this study, Mn_0.5Zn_0.5Ag_3xFe_2-xO₄ (x ≤ 0.08) nanospinel ferrites were synthesized via a sol–gel route to investigate the influence of Ag on structure, cation distribution, magnetic behavior, and charge transport. X-ray diffraction confirmed a cubic spinel phase with crystallite sizes ranging from 18.1 nm (x = 0.02) to 26.4 nm (x = 0.00), accompanied by lattice expansion due to Ag ⁺ incorporation at octahedral sites. Mössbauer spectroscopy revealed Fe³⁺ site redistribution and the presence of a minor α-Fe₂O₃ phase starting from x = 0.02. Magnetic measurements showed a non-monotonic variation in saturation magnetization, peaking at 209.29 emu/g (RT) for x = 0.02, linked to optimized Fe³⁺–O^2-–Fe³⁺ superexchange and secondary phase effects, while all samples exhibited soft magnetic nature at 10 K. AC conductivity followed Jonscher's law, with the lowest activation energy (Ea) (0.39 eV) for the undoped ferrite and maximum conductivity at x = 0.06 due to enhanced Fe²⁺/Fe³⁺ hopping. Dielectric analysis indicated Maxwell–Wagner interfacial polarization with composition-dependent trends, and impedance spectroscopy confirmed dual grain and grain-boundary relaxation. These findings establish Ag substitution as an effective means to engineer the coupled magnetic–dielectric response of Mn–Zn ferrites, enabling application-specific tuning in soft magnetic and spintronic systems.