Electronic and magnetic properties of 3d transition-metal atom adsorbed graphene and graphene nanoribbons

In this paper, we theoretically studied the electronic and magnetic properties of graphene and graphene nanoribbons functionalized by 3d transition-metal (TM) atoms. The binding energies and electronic and magnetic properties were investigated for the cases where TM atoms adsorbed to a single side and double sides of graphene. We found that 3d TM atoms can be adsorbed on graphene with binding energies ranging between 0.10 and 1.95 eV depending on their species and coverage density. Upon TM atom adsorption, graphene becomes a magnetic metal. TM atoms can also be adsorbed on graphene nanoribbons with armchair edge shapes (AGNR's). Binding of TM atoms to the edge hexagons of AGNR yields the minimum energy state for all TM atom species examined in this work and in all ribbon widths under consideration. Depending on the ribbon width and adsorbed TM atom species, AGNR, which is a nonmagnetic semiconductor, can either be a metal or a semiconductor with ferromagnetic or antiferromagnetic spin alignment. Interestingly, Fe or Ti adsorption makes certain AGNR's half-metallic with a 100% spin polarization at the Fermi level. Present results indicate that the properties of graphene and graphene nanoribbons can be strongly modified through the adsorption of 3d TM atoms.