Prediction of manganese trihalides as two-dimensional Dirac half-metals

The recent discovery of intrinsic ferromagnetism in two-dimensional (2D) van der Waals crystals down to the monolayer limit has sparked intense interest due to their potential applications in spintronics. Here, using first-principles calculations we predict that the 2D pristine MnX3 (X = F, Cl, Br, I) is a family of intrinsic Dirac half-metals characterized by a band structure with an unusually large gap in one spin channel and a Dirac cone in the other with carrier mobilities comparable to those in graphene. We demonstrate that the MnX3 are dynamically and thermodynamically stable up to high temperatures, and exhibit large magnetic moments of about 4 mu(B) per Mn3+ ion, high Curie temperatures, and large in-plane magnetic anisotropy energy. In addition, the gap opening induced by the spin-orbit coupling drives the lighter systems into the quantum anomalous Hall state. The combination of these unique properties renders this class of 2D ferromagnets a promising platform for high efficiency spintronic applications.