Synthesis and characterisation of MxFe3-xO4 (M = Fe, Mn, Zn) spinel nanoferrites through a solvothermal route

Given the technical hurdles associated with the thermal decomposition method for the synthesis of monodisperse nanocrystals, metal spinel nanoferrites MxFe3-xO4 (M = Fe, Mn, Zn) were prepared by the solvothermal method. Structural, morphological and magnetic characterisations were completed using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), energy-dispersive spectroscopy (EDS), atomic absorption spectroscopy (AAS), vibrating sample magnetometry (VSM) and X-ray photoelectron spectroscopy (XPS) techniques. The size of the synthesised nanoferrites spanned from 7 to 16 nm based on TEM results. EDS, AAS and XPS evidenced successful doping of Zn2+ and Mn2+ into the Fe3O4 structure. XRD revealed the expansion of the cell unit of Fe3O4 with the substitution of the larger Zn2+ and Mn2+ ions. All prepared nanoferrites presented with superparamagnetism at room temperature (300 K) with a blocking temperature less than room temperature (T-B < T).