2D Magnetic MXenes (M1_1-M2)₃C₂ (M1 = V, Cr; M2 = Mn, Cr): The Stability, Ordering, and Magnetic Properties

Since their discovery in 2011, the MXene family of two-dimensional (2D) materials has attracted much interest due to its unique properties, leading to practical applications. Recently, special attention has been paid to magnetic MXenes. However, despite the great diversity of the chemical composition of MXenes, which opens up prospects for obtaining magnetic 2D materials, only a few MXenes with intrinsic magnetism have been synthesized to date. The main reason for this is the phase instability of both MXenes and their parent MAX phases. Here, we use the first-principles calculations and the cluster expansion (CE) method to analyze the thermodynamic stability of second-order MXenes (M1_1- M2)₃C₂ and their parent MAX phases with two transition metals (M1 = V, Cr; M2 = Mn, Cr). Our analysis allows us to identify the most stable MXene structures with possible magnetism. In the stable structures found, the electronic and magnetic properties were calculated. The effect of surface functionalization with fluorine and oxygen on the properties of the MXenes was also studied. It was found that the most promising for synthesis is (V_1/3Mn_2/3)₃C₂, which is ferromagnetic with a large magnetic moment per cell, both in bare form and with functionalization of its surface with fluorine.