Defect-induced bipolar magnetism in atomically thin GeS

Two-dimensional (2D) materials offer exciting prospects for spintronic applications, yet most lack intrinsic magnetism. Here, we investigate hydrogen adsorption on monolayer germanium monosulfide (GeS) and its impact on the electronic and magnetic properties using density functional theory and first-principles-based typical medium dynamical cluster approximation (TMDCA). Our results reveal that hydrogen adsorption at Ge-top and S-top sites induces localized magnetic moments by introducing spin-polarized impurity states within the bandgap. Charge transfer and hybridization between H-1s, Ge-4s, Ge-4p, and S-3p orbitals drive the formation of these states, with Ge-top adsorption exhibiting stronger localization and stability. Exchange interactions reveal a robust antiferromagnetic (AFM) ordering, with stripe-like spin alignment favored at a critical hydrogen concentration. Below this concentration (∼1.95% of H concentration), the stripe AFM order transitions into a ferromagnetic configuration, wherein the system exhibits a bipolar magnetic semiconductor character, with the spin-up and spin-down states symmetrically straddling the Fermi level. This enables 100% spin filtration at multiple energy levels, including the pristine GeS band edges. Furthermore, we examine the role of native Ge vacancies using TMDCA, showing that increasing vacancy concentration suppresses the magnetic moment as Ge vacancies introduce shallow acceptor states that delocalize hydrogen-induced impurity states. These findings highlight hydrogen functionalization as an effective strategy for engineering and modulating magnetism in non-magnetic 2D GeS semiconductors and provide insight into defect-tunable spintronics for next-generation low-dimensional spin-based devices.