Tuning Electronic and Magnetic Properties of Monolayer MnPSe₃ via Surface Adsorption

The engineering of magnetic order and electronic states in two-dimensional (2D) materials is pivotal for advanced spintronic technologies. Despite their potential, the scarcity of intrinsic 2D ferromagnetic and ferrovalley materials remains a critical challenge. Here, we employ density functional theory with Hubbard-U corrections to systematically investigate adsorbate-driven magnetic transitions in monolayer MnPSe3. While pristine MnPSe3 exhibits antiferromagnetic (AFM) ordering with a semiconducting gap, Li and F adsorption at coverages of 33–100% induces an AFM-to-ferromagnetic (AFM–FM) transition, whereas only full (100%) O adsorption yields the same magnetic phase change. Our calculations reveal enhanced thermodynamic stability at elevated coverages, with full-coverage configurations (Li0.5MnPSe3, MnPSe3O0.5, MnPSe3F0.5) favored energetically. Hybrid functional (HSE06) calculations show that F adsorption drives a semiconductor-to-half-metal transition, whereas Li and O adsorption preserves the semiconductivity. Moreover, Li adsorption breaks the MT symmetry protecting the K/K′ degeneracy in MnPSe3, and when spin–orbit coupling is included, it induces a 20.3 meV valley splitting in the valence band, thereby rendering Li0.5MnPSe3 an intrinsically valley-polarized FM semiconductor. Crucially, carrier doping results indicate that once the electron doping concentration reaches 8.3 × 1013 cm–2, the magnetic easy axis of monolayer MnPSe3 transitions from in-plane to out-of-plane. This work establishes atomic adsorption as a robust strategy for tailoring 2D magnetism, resolving discrepancies through the rigorous treatment of exchange-correlation effects and configurational diversity.