Adatoms in graphene as a source of current polarization: Role of the local magnetic moment

We theoretically investigate spin-resolved currents flowing in large-area graphene, with and without defects, doped with single atoms of noble metals (Cu, Ag, and Au) and 3d-transition metals (Mn, Fe, Co, and Ni). We show that the presence of a local magnetic moment is a necessary but not sufficient condition to have a nonzero current polarization. An essential requirement is the presence of spin-split localized levels near the Fermi energy that strongly hybridize with the graphene pi bands. We also show that a gate potential can be used to tune the energy of these localized levels, leading to an external way to control the degree of spin-polarized current without the application of a magnetic field.