Defect‐Mediated Magnetic Exchange and Charge Transport in Hydrothermally Synthesized Zn 0.2 Mn 0.8 Fe 2 O 4 Spinel Nanoferrite

Zn 0.2 Mn 0.8 Fe 2 O 4 nanocrystalline ferrite was synthesized via a hydrothermal route to investigate the influence of oxygen‐vacancy defects on its magnetic and electrical transport properties. X‐ray diffraction confirmed a cubic spinel structure (Fd3̅m) with a minor α‐Fe 2 O 3 secondary phase. Electron microscopy revealed rod‐like nanostructures, while Raman spectroscopy confirmed the characteristic vibrational modes of the spinel lattice. X‐ray photoelectron spectroscopy identified mixed Fe 2+ /Fe 3+ valence states together with Zn 2+ and Mn 2+ ions, indicating oxygen‐vacancy‐induced charge compensation. Defect‐related energy levels was further supported by photoluminescence analysis. Magnetic measurements exhibited soft ferrimagnetic behavior with a saturation magnetization of 53.21 emu/g and a coercivity of 0.06 kOe. The experimentally observed magnetic moment was significantly lower than that predicted by Néel's two‐sublattice model, suggesting the contribution of surface spin canting, finite‐size effects, and weakened A–B superexchange interactions induced by Zn substitution. Impedance spectroscopy demonstrated grain‐boundary‐dominated non‐Debye relaxation behavior, while the electrical conductivity followed Arrhenius‐type thermally activated conduction with an activation energy of 0.59 eV. The charge transport mechanism is attributed to small‐polaron hopping between Fe 2+ and Fe 3+ ions. The results establish a strong correlation between oxygen‐vacancy defects, magnetic exchange interactions, and charge transport in Zn‐substituted manganese ferrite, highlighting its potential for multifunctional magnetic and electronic applications.