Preparation of magnetic nanocrystalline Mn0.5Mg0.5Fe2O4 and kinetics of thermal decomposition of precursor

Abstract

The spinel Mn0.5Mg0.5Fe2O4 was obtained via calcining Mn0.5Mg0.5Fe2(C2O4)3·5H2O above 400 °C in air. The precursor and its calcined products were characterized by thermogravimetry and differential scanning calorimetry, Fourier transform FT-IR, X-ray powder diffraction, scanning electron microscopy, energy dispersive X-ray spectrometer, and vibrating sample magnetometer. The results showed that Mn0.5Mg0.5Fe2O4 obtained at 600 °C had a specific saturation magnetization of 46.2 emu g–1. The thermal decomposition of Mn0.5Mg0.5Fe2(C2O4)3·5H2O below 450 °C experienced two steps which involved, at first, the dehydration of five water molecules and then decomposition of Mn0.5Mg0.5Fe2(C2O4)3 into spinel Mn0.5Mg0.5Fe2O4 in air. Based on Starink equation, the values of the activation energies associated with the thermal decomposition of Mn0.5Mg0.5Fe2(C2O4)3·5H2O were determined.