Ab initio investigations of a CoBiS monolayer with and without point defects

Through density functional theory (DFT) calculations, a new triclinic monolayer, namely CoBiS, with higher stability than that of penta-CoBiS, is predicted. Our results show that this monolayer is a nonmagnetic metallic compound. To tune its magnetic properties, we systematically investigated the formation and energetics of different point defects in the CoBiS monolayer, such as V_Bi, V_S and V_Co. We find that the monolayer becomes magnetic with the different points defects. Our calculated magnetic anisotropy energy (MAE) indicated that V_Bi and V_S exhibit out-of-plane MAE, while the MAE is in-plane for V_Co. By solving the Heisenberg model using the Monte Carlo simulation method, we obtain transition temperatures for V_S and V_Co systems much larger than room temperature, implying potential applications in spintronic devices.