Thermomagnetometric evidence of γ-Fe2O3 as an intermediate in the oxidation of magnetite

The oxidation of magnetite, Fe3O4, to hematite, α-Fe2O3 was followed by thermogravimetry (TG), both with and without a small magnetic field gradient imposed upon the sample. The results of this thermomagnetometry (TM) clearly indicates the formation of a strongly magnetic intermediate during the oxidation process. This intermediate reaches a maximum concentration at about 270 °C and disappears by approximately 320 °C. This confirms the speculation that γ-Fe2O3 is as an intermediate in this oxidation process [J. Therm. Anal. Calorim. 73 (2003)].