Synthesis of phase pure iron oxide polymorphs thin films and their enhanced magnetic properties

The α-Fe₂O₃ thin film was prepared on liquid–vapor interface at room temperature by a facile and cost effective method, which was converted to Fe₃O₄ and γ-Fe₂O₃ films by reduction and oxidation process. The morphological and structural characterizations reveal the average crystallites size in α-Fe₂O₃, Fe₃O₄ and γ-Fe₂O₃ films 12.8, 9.2 and 19 nm with rms roughness 4.35, 4.60 and 8.21 nm, respectively. From magnetic measurements, the α-Fe₂O₃ thin film shows a room temperature super-paramagnetic behavior with saturation magnetization 18 emu/cm³, while Fe₃O₄ and γ-Fe₂O₃ thin films exhibit ferrimagnetic behavior with saturation magnetization values 414.5 and 148 emu/cm³, respectively. A significantly higher value of saturation magnetization is observed in α-Fe₂O₃ film, which is trusted due to the uncompensated surface spins in the film. The converted Fe₃O₄ film also shows enhanced saturation magnetization due to the reduction in antiphase boundaries, whereas the magnetization in γ-Fe₂O₃ film decreases comparatively. The magnetic property of the γ-Fe₂O₃ is explained on the basis of the Fe³⁺ ions vacancy at the octahedral position in its structure.