Room-temperature ferromagnetic half-metallicity of two-dimensional oxyhalides CrOX2 (X = F, Cl) monolayers

Two-dimensional (2D) materials with room-temperature ferromagnetism and intrinsic wide half-metallic gap are superb candidates for pure spin generation, injection, and transport in nanospintronic applications. In this work, we disclose the magnetic and electronic properties of 2D transition metal oxyhalides CrOX2 monolayers and the effect of strain on them using first-principles calculations. Our results show that CrOX2 (X = F, Cl) exhibits intrinsic ferromagnetism and half metallicity with the half-metallic gap of more than 2 eV, as well as the phase transition temperature over 300 K when considering the Hubbard Ueff correction as 3.5 eV as obtained in most chromium oxide. Uniaxial strain can drive magnetic phase transition occur and the phase transition temperature enhance greatly. In addition, we also find that CrOF2 monolayer is mechanically, thermally and dynamically stable, but the CrOCl2 monolayer is only mechanically and thermally stable. These excellent properties of CrOX2 monolayers, in particular, CrOF2, make them hopeful for the fabrication of nanospintronic devices operating at room temperature.