Magnetic coupling between 3d transition metal adatoms on graphene supported by metallic substrates

The role of a metallic substrate in the interaction between 3d transition metal magnetic atoms adsorbed on graphene is explored for Ir(111), Cu(111) and Ni(111) surfaces. As a general rule, we find that exchange coupling between impurities is essentially determined by the graphene layer and it varies smoothly along the series of 3d atoms for Ir(111) and Cu(111) surfaces, except when resonances appear close to the Fermi level. This universal behavior is at the heart of our main conclusion: the weak interaction between graphene and the underlaying Ir and Cu metal surfaces does not alter appreciably the coupling between magnetic impurities. Therefore, we dare to speculate that previous results based on calculations with freestanding graphene are physically sound and correct. However, in the case of Ni(111) additional effects appear due to the metal surface magnetization.

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