Influence of Mg doping on the structural, magnetic, optical, and electrical properties of Co–Zn spinel ferrites

Abstract The effect of Mg substitution on the structural, vibrational, optical, magnetic, dielectric, and electrical properties of cobalt–zinc ferrite was systematically investigated using Co₀.₅Zn₀.₅₋ₓMgₓFe₂O₄ (x = 0.0–0.5) ceramics synthesized by the sol–gel method. X-ray diffraction and Rietveld refinement confirmed the formation of a single-phase cubic spinel structure (space group Fd3̅m) for all compositions. Structural parameters, including cation–cation and cation–anion distances, were systematically analyzed, revealing crystallite sizes in the range of 13.47–25.92 nm. FTIR spectra exhibited characteristic absorption bands near 650 and 460 cm⁻¹, corresponding to tetrahedral and octahedral metal–oxygen vibrations, accompanied by slight reductions in bond length, force constant, and Debye temperature. Optical analysis revealed a gradual decrease in the band gap from 1.72 to 1.43 eV with increasing Mg content, indicating modifications in the electronic structure. Magnetic measurements confirmed ferromagnetic behavior with a multidomain nature, while a single-peak switching field distribution indicated uniform magnetization reversal. The Co₀.₅Zn₀.₅Mg₀.₅Fe₂O₄ composition exhibited the highest saturation magnetization among all Mg-substituted samples. Dielectric studies demonstrated that this composition possessed a high dielectric constant with comparatively low dielectric loss. Impedance and modulus analyses revealed non-Debye relaxation behavior, whereas Nyquist plots confirmed the contributions of both grains and grain boundaries to the electrical conduction process. These findings demonstrate that Mg substitution effectively tailors the multifunctional properties of Co–Zn ferrites, making Co₀.₅Zn₀.₅Mg₀.₅Fe₂O₄ a promising material for high-frequency electronic and memory device applications.