Impurity band driven ferromagnetism in nonmetal-doped holey graphyne

The emergence of two-dimensional magnetic carbon materials offers a promising platform for spintronic applications. However, pristine carbon materials typically exhibit nonmagnetic behavior. In this work, we investigate the magnetic properties of holey graphyne (HGY) doped with nonmetal sp-impurity atoms (B, N, P, and S) via adsorption and substitution. First-principles calculations reveal that specific doping configurations exhibit spontaneous ferromagnetism driven by narrow impurity bands at the Fermi level. Among them, the Curie temperatures of the P-adsorbed HGY (H2 site) and P-substituted HGY (T2 site) reach 200 K and 104 K, respectively. Notably, for P-substituted HGY (T2 site), the magnetic moments primarily originate from the sp-hybridized carbon atoms adjacent to the impurity rather than from the impurity itself, thereby enhancing the chemical reactivity of the carbon atoms. Furthermore, reducing the substitutional doping concentration to approximately 1% enhances $\ensuremath{\pi}$-electron localization and narrows the impurity bandwidth, forming isolated and nonoverlapping impurity bands, which promotes spin polarization of the system. Under low doping conditions, all doped structures exhibit ferromagnetic ground states. These findings propose a tunable strategy for achieving magnetism and bipolar magnetic semiconducting behavior in carbon-based 2D semiconductors, paving the way for lightweight carbon-based spintronic devices.