2D-Double transition metal MXenes for spintronics applications: surface functionalization induced ferromagnetic half-metallic complexes

MXenes are rapidly emerging two-dimensional (2D) materials with thickness, composition, and functionalization-dependent outstanding properties having applications in diverse fields. To disclose the nano-spintronic applications of 2D-double transition metal (DTM) carbide and nitride-based pristine and surface-functionalized MXenes (M-2'M '' X2Tx, M' and M '' = Cr, Mo, W; X = C/N; T = -F/-OH/=O), a systematic investigation has been performed on their structural stability, magnetic properties and electronic structure using spin-polarized first-principles calculations. 36 stable functionalized MXenes were screened from 144 explored DTM based MXenes. The explored materials exhibit striking properties, having a wide range of magnetic ground states, from non-magnetic to ferromagnetic, and then to antiferromagnetic, accompanied by metallic to half-metallic or gapless half-metallic properties, depending on the transition metal(s) and terminating group. Mo and W-based MXenes are found to be nonmagnetic and metallic, whereas Cr-Mo and Cr-W-based MXenes are magnetic with varying metallic behavior. W2CrN2O2 and Mo2CrN2O2 systems are found to be ferromagnetic half-metallic 2D materials with a direct band gap of 1.35 eV and 0.77 eV respectively, in the minority spin channel. A comprehensive study on DTM MXenes, which show intrinsic half-metallic properties along with robust ferromagnetism, opens up a class of promising new 2D materials with tunable magnetic and electronic properties for potential device applications in nano-spintronics and electronics.