Intrinsic ferromagnetism and the quantum anomalous Hall effect in two-dimensional MnOCl2 monolayers

Due to their potential application in spintronic devices, two-dimensional (2D) ferromagnetic materials are highly desired. We used first-principles calculations and Monte Carlo simulations to investigate the electronic structure and magnetic characteristics of the MnOCl2 monolayers. We discovered two stable monolayer structures, Pmna-MnOCl2 and Pmmn-MnOCl2. Our findings show that the Pmna-MnOCl2 monolayer is an intrinsic ferromagnetic semiconductor with an indirect band gap of 0.152 eV and a Curie temperature (T-C) of 202 K, while the Pmmn-MnOCl2 monolayer is an intrinsic ferromagnetic Dirac semimetal with a high T-C (910 K) and triaxial magnetic anisotropy. We also show that a Pmmn-MnOCl2 monolayer with a nontrivial band gap of 6.2 meV can achieve the quantum anomalous Hall effect (QAHE) with Chern number C = 1. Additionally, the existence of a gapless edge state can be flexibly regulated by choosing the terminal edges. Our studies reveal that the Pmmn-MnOCl2 monolayer can serve as a candidate material to achieve high-temperature QAHE.