3d-level symmetry between metal layers governing the electronic configuration of Mn₂N MXenes and enabling modulation between half-metallicity and semiconductivity

MXenes, composed of transitionmetal layers with various surface passivation groups, exhibit diverse magnetic and electron transport properties essential for miniaturized spintronic devices. Through density functional theory calculations, we reveal that the electronic properties of Mn2NOT (T = O, F, OH, Cl) MXenes, i.e., half-metallicity and semiconductivity, are determined by the energy-level separation between two side Mn atoms arising from the distinctive two-surface passivation, in contrast to other typical 2D magnetic materials like transition metal dichalcogenides that are determined by the local metallic atom coordination symmetry. The separation degree of energy levels decides the electron configuration of Mn 3d orbitals and the Fermi-level position, thereby determining the half-metallicity or semiconductivity. This mechanism enables dynamic control methods for tuning electronic and magnetic properties. For instance, charge (electron or hole) doping and applying uniaxial strain can drive transitions between semiconductor and half-metal states by modulating the Mn energy levels, Mn-N electrostatic potential, and Mn 3d orbitals filling at two surface sides. Our findings reveal the physical origins of MXenes’ electromagnetic properties and offer strategies for designing tunable and highly integrated spintronic devices.