BaFeO3 cubic single crystalline thin film: A ferromagnetic insulator

We have synthesized BaFeOx thin films by pulsed-laser deposition followed by low temperature (200 °C) oxidation to BaFeO3. X-ray diffraction indicates that fully oxidized single crystalline BaFeO3 has been formed with a lattice parameter of 3.97 Å, the bulk stoichiometric value. The oxidation state of Fe is confirmed to be 4+ by using hard x-ray photoemission spectroscopy. A ferromagnetic ground state is found with saturation magnetization and Curie temperature of 3.2 μB/formula unit and 115 K, respectively. Unusually, for a uniform cubic ferromagnet, the films are insulating with an optical gap of ∼1.8 eV.