Facile synthesis, characterization and magnetic properties of manganese ferrite/carbon composites

Manganese ferrite/carbon (MnFe2O4/C) composites were prepared by the thermal decomposition of Mn(NO3)2-Fe(NO3)3-polyvinyl alcohol (PVA) gels with different PVA content. Thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) as well as the Fourier-transform infrared spectroscopy (FTIR) confirmed the redox interaction between PVA and nitrate ions at around 100 °C. The effect of experimental conditions such as annealing temperature, reaction atmosphere (air, nitrogen), opened or covered crucibles for obtaining manganese ferrite as single crystalline phase was investigated. Manganese ferrite as single crystalline phase was obtained by annealing the precursor in air at 400 °C for 3 h in covered crucibles. The saturation magnetization of MnFe2O4/C composites decreased with the increase of the carbon amount from 47.9 emu g−1 to 18.5 emu g−1 and was correlated with the PVA content. The saturation magnetization of the sample with the highest carbon content increased from 0.1 emu g−1 to 24.6 emu g−1 by growing the annealing temperature from 300 to 600 °C.