Magnetic Properties of the Dual Oxide System CuO–Fe2O3

It has been demonstrated that hydrous ferric oxide and cupric oxide gels consist of very small particles and contain magnetically dilute Fe3+ and Cu2+ ions, respectively. Heating or aging these gels produces an increase in particle size with the onset of crystalline magnetic interactions. Coprecipitated samples of these oxides contain no CuFe2O4 when merely air-dried or heated at 170°C, but consist of mixtures of CuO and α-Fe2O3. Higher heat-treatment of these samples up to 900°C results in mixtures of CuFe2O4 and/or α-Fe2O3 and CuO, with the amount of CuFe2O4 increasing with temperature of heat-treatment. Heat-treatment at 1100°C produces a solid solution of CuF2O4 and γ-Fe2O3 in the range greater than 40 mole % Fe2O3. Analysis of the ferrimagnetic magnetization and Curie points suggest that γ-Fe2O3 has a Curie point of 625°C and a magnetization of 65.0 emu/g. The results are consistent with cationic distribution of Fe[Fe5/3□1/3]O4 and Fe[CuFe]O4.