Metal-insulator transition temperature in EuO1−x films as a function of exposure time in air

Oxygen-deficient Europium monoxide EuO _1−x shows a metal-to-insulator transition near the Curie temperature (T _C). A systematic transport study of EuO _1−x thin films as a function of exposure time in air reveals a gradually decreased T _C from 140 K to 70 K as the concentration of the oxygen vacancies decreases, which is accompanied by a drastic increase in the resistance. We also find an unusual enhancement of magnetic anisotropy in the transport measurements, which results from the strong spin-orbit coupling at the interface between the film and substrate and possible presence of spin-textures like skyrmions in EuO _1−x.