Hydrogen saturation stabilizes vacancy-induced ferromagnetic ordering in graphene

Density functional theory calculations are performed to explore vacancy-induced magnetism in graphene. The hydrogen saturation not only stabilizes the vacancy structure but also induces distinct magnetic coupling depending on the defect distribution: weak magnetic coupling between defects on different sublattices and strong coupling between defects on the same sublattice. Ferromagnetic ordering has to be accompanied with a semiconducting property. The interaction integral J between defective spins decreases linearly with the increase of the distance between them. Based on the 2D Ising model and Monte Carlo simulations, the possible highest Curie temperature T-c of defective graphene is predicted to be lower than 500 K.