Strong magnetic anisotropy of chemically bound Co dimers in a graphene sheet

The magnetism of cobalt atoms and dimers bound by single vacancies in a graphene sheet is investigated by means of relativistic density functional calculations. In both cases, local magnetic moments are formed despite strong chemical binding. While orbital magnetism is suppressed in the Co atoms, magnetic bistability with an anisotropy barrier of about 50 meV is possible in the chemically bound Co dimers. The feasibility of their preparation is demonstrated and a general construction principle for similar (sub-)nanometer size magnets is proposed. DOI: 10.1103/PhysRevB.86.235430