High Curie temperature and large perpendicular magnetic anisotropy in two-dimensional half metallic OsI3 monolayer with quantum anomalous Hall effect

The 5 d transition heavy elements with large spin-orbit coupling (SOC) effect can induce a large magnetic anisotropy energy (MAE) in magnetic materials. Meanwhile, the asymmetric occupation of 5 d orbital electrons in transition metal trihalides can also trigger interesting orbital ordering. Here, the electronic structure and magnetic properties of two-dimensional (2D) OsI 3 monolayer were investigated by first-principles calculations. The OsI 3 monolayer has two orbital orderings with low spin states, where the half-metallic state is an Ising ferromagnet with a Curie temperature ( T C ) of 208 K and a perpendicular magnetic anisotropy (PMA) of −45.8 meV, but the Mott insulator state has an in-plane magnetic anisotropy (IMA) of 13.7 meV. The half-metallic state included non-self-consistent SOC calculations opens a band gap of 118.3 meV, showing a quantum anomalous Hall effect (QAHE) with a Chern number ( C ) of −1. A topologically trivial band gap opened in self-consistent SOC calculations, where QAHE of C = −2 can be realized by shifting Fermi surface. The in-plane biaxial strain can significantly tailor the MAE of the half-metallic state, yielding a PMA of −33.0 and −50.7 meV at a compressive strain of 6% and −2%. Meanwhile, T C rises to 275 K at a tensile strain of 6%. The transition between Mott insulator and half-metallic states can also be regulated by strain. These findings suggest that OsI 3 monolayer is promising for 2D magnetism and spintronics. • Obtained two electronic configurations of half-metallic and Mott insulator states. • T C of 208 K in half-metallic state can be raised to 275 K at a strain of 6%. • The half-metallic state opens a topologically nontrivial gap by spin orbital coupling. • Strain can tailor PMA of half-metallic state, achieving a change from −33.0 meV at 6% strain to −50.7 meV at −2% strain.