Carrier-induced antiferromagnet of graphene islands embedded in hexagonal boron nitride

Graphene islands with zigzag edges embedded in nitrogen-terminated vacancies in hexagonal boron nitride are shown to develop intrinsic magnetism and preferentially order antiferromagnetically. The magnetic moment of each graphene island is given by the numerical imbalance of carbon atoms on its two sublattices, which is in turn directly related to the size of the host defect. We propose a carrier-mediated model for antiferromagnetic coupling between islands and estimate Neel temperatures for these structures in excess of 100 K in some instances, with the possibility of attaining even higher temperatures at higher island densities. Our results suggest the possibility of designing molecular magnets via defect engineering of hexagonal boron nitride templates followed by trapping of carbon atoms in the defects.