Tunable valley splitting and magnetic anisotropy in two-dimensional buckled honeycomb lattice Mn2X2 (X = F, Cl, Br).

Compared to ferromagnetic materials that realize valley splitting via time-reversal symmetry breaking and spin-orbit coupling, the realization of spontaneous valley splitting in monolayer antiferromagnetic materials remains less explored. Here, based on first-principles calculations and effective model analysis, we demonstrate that the antiferromagnetic monolayer Mn2X2 (X = F, Cl, Br) exhibits prominent valley splitting, making it a promising candidate for ferrovalley applications. Specifically, the energy difference of the valence band maximum at the K and K' points reaches 38.539 meV, while the conduction band minimum displays a valley splitting of -21.684 meV. This spontaneous valley splitting originates from the spin-polarized Mn-d orbitals. Importantly, the valley splitting can be effectively tuned via biaxial strain and the on-site Hubbard U interaction, providing versatile knobs for manipulating valleytronic functionalities. Our results not only expand the scope of anomalous valley Hall physics in antiferromagnets but also offer a practical strategy for realizing low-power valley-based devices using two-dimensional materials.