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

The alpha-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 gamma-Fe2O3 films by reduction and oxidation process. The morphological and structural characterizations reveal the average crystallites size in alpha-Fe2O3, Fe3O4 and gamma-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 alpha-Fe2O3 thin film shows a room temperature super-paramagnetic behavior with saturation magnetization 18 emu/cm(3), while Fe3O4 and gamma-Fe2O3 thin films exhibit ferrimagnetic behavior with saturation magnetization values 414.5 and 148 emu/cm(3), respectively. A significantly higher value of saturation magnetization is observed in alpha-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 gamma-Fe2O3 film decreases comparatively. The magnetic property of the gamma-Fe2O3 is explained on the basis of the Fe3+ ions vacancy at the octahedral position in its structure.