Oxidation process of Fe films under atmospheric conditions is depth limited such that an oxide covering layer with a well-defined thickness is formed by which the underlying metal is prevented from further oxidation. Iron thin film with an initial thickness d_{i}=4 nm was deposited onto 1.6 nm - V(110) buffer layer using UHV magnetron sputtering. The planar growth of Fe oxides was revealed by atomic force microscopy. X-ray photoelectron spectroscopy studies performed after 250 days of oxidation revealed formation of a hematite (α-Fe₂O₃) ultrathin film on the metallic rest of iron. Furthermore, low temperature magnetic measurements of the oxidised Fe ultrathin film revealed an exchange anisotropy which is imposed to the metallic rest. As a result, we have observed at low temperatures a shift and broadening of the hysteresis loops due to the exchange interaction at the metal-oxide interface.
We have studied oxidation kinetics of Fe thin film under atmospheric conditions using the fact that metallic iron is a ferromagnet but ultrathin natural iron oxides are approximately nonmagnetic at room temperature. As a consequence, oxidation is associated with a loss in total Fe magnetic moment. Results show that the sample with an initial Fe thickness equal to 10 nm oxidize relatively fast (time constant τ=0.05 day), whereby a constant amount of 2.5 nm of metal is transformed into oxides. For lower iron initial thickness (d_{i}=4 nm) the time constant for oxidation significantly increases reaching a value of 2 days. Furthermore, X-ray photoelectron spectroscopy studies performed after 144 days of oxidation revealed formation of hematite (α-Fe₂O₃) thin film on the metallic rest of iron.
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