Reversible oxidation–reduction of epitaxial iron oxide films on Pt(111): Magnetite–hematite interconversion Available to Purchase

We studied magnetite–hematite–magnetite transformations in an ultrathin epitaxial film on Pt(111) using surface sensitive and bulk sensitive methods. At initial oxidation stages at elevated temperature (810 K), a 5-nm thick magnetite Fe₃O₄(111) film became non-stoichiometric toward maghemite and then showed the first signs of hematite phase formation under an oxygen exposure of 3 × 10³ L. Finally, under 2 × 10⁴ L, the film fully transformed to hematite α-Fe₂O₃(0001), maintaining a high single-crystal quality. A comparison of the conversion electron Mössbauer spectra and low energy electron diffraction pattern showed that at intermediate oxidation stages, hematite dominated at the surface, whereas a spinel phase was still observed in the deeper layers. The magnetite–hematite conversion was fully reversed by annealing under ultra-high vacuum at temperatures exceeding 600 K, and despite a change in morphology, the magnetite film preserved the original crystal structure and orientation.