Microstructure and optical properties of pulsed-laser-deposited iron oxide films

We have grown epitaxial iron oxide films on MgO substrates using pulsed laser deposition. In the wavelength range of 0.3-2 μm, the refractive index was 2.5±0.2 and the absorption coefficient was in the range of 5-16 μm^-1, with a minimum at a 0.87-μm wavelength. Absorption peaks were fitted at 0.33±0.01 μm, 0.54±0.04 μm, and 1.78±0.15 μm wavelengths. The Faraday rotation of the films was 4°/μm at 0.645 μm and 2.5°/μm at 1.55 μm. Both the high Faraday rotation and the high absorption, in addition to a significant electrical conductivity, are most probably the result of Fe²⁺ ions present in the γ-Fe₂O₃ films deposited in vacuum.