Highly anisotropic magnetic states of Co dimers bound to graphene-vacancies

The adsorption behavior and the magnetic states of cobalt atoms and dimers on single vacancies in a graphene sheet are investigated by means of relativistic density functional calculations. It is found that local magnetic moments are formed in both cases, despite strong chemical binding. Of particular interest are kinetically stable isomers with two cobalt atoms attached to the same side of the graphene sheet. Magnetic bi-stability with an anisotropy barrier of about 50 meV is possible in this geometry. The feasibility of its preparation is discussed.