Intrinsic ferromagnetism and quantum anomalous Hall effect in a CoBr monolayer.

The electronic, magnetic, and topological properties of a CoBr monolayer are studied in the framework of density-functional theory (DFT) combined with tight-binding (TB) modeling in terms of the Wannier basis. Our DFT investigation and Monte Carlo simulation show that there exists intrinsic two-dimensional ferromagnetism in the CoBr monolayer, thanks to the large out-of-plane magnetocrystalline anisotropic energy. Our further study indicates that the spin-orbit coupling makes it become a topologically nontrivial insulator with a quantum anomalous Hall effect and topological Chern number [script C] = 4 and its edge states can be manipulated by changing the width of its nanoribbons and applying strains. The CoBr monolayer can be exfoliated from the layered CoBr bulk material because its exfoliation energy is between those of graphene and the MoS monolayer and it is dynamically stable. These results make us believe that the CoBr monolayer can make a promising spintronic material for future high-performance devices.