Structural, optical electrical and magnetic properties of Zn0.5Mg0.5Fe2O4 ferrite

Although spinel ferrites find applications in different fields, their multifunctionality can be improved by substitution in each site. The insertion of different transition metals in this fmily of compounds tailors the electrical and magnetic properties. In this study, nano-sized powders of ZnFe2O4 doped with Mg2+ transition metal ions are synthesized by the solid-state reaction method, with a sintering step at 1200 degrees C. X-ray diffraction analysis confirms that the resulting structure is cubic, belonging to the Fd3m space group, and exhibits a single-phase with crystallite size of around 35 nm. Optical properties are studied by UV-visible spectroscopy, revealing a direct transition with a bandgap of 3.71 eV. Impedance spectroscopy reveals a thermally activated DC conductivity with an activation energy of 223 meV, while the corroleated barrier hopping (CBH) modelexplained the conduction mechanism in AC regims. Analysis of the Nyquist plots shows the contribution of grains and grain boundaries to the material's electrical response. The magnetic study evidences a transition between a ferrimagnetic state at low temperature and a superparamagnetic state at room temperature, with a blocking temperature around 80 K. High coercivity and remanent magnetization reflect a stable magnetic order. We deduce that the substitution of Zn by Mg influences the cation distribution and favors superparamagnetism at high temperatures. These results suggest that Zn0.5Mg0.5Fe2O4is interesting for use in optoelectronic and magnetic devices.