Magnetic Properties of the Dual Oxide System CuO–Fe2O3

Abstract

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[Fe_5/3□_1/3]O₄ and Fe[CuFe]O₄.