Spin-filtering in graphene junctions with Ti and Co adsorbates

The accurate theoretical modeling of a nanojunction made of a single graphene sheet with regularly adsorbed Ti or Co atoms is presented in the context of spintronic applications. Our calculation show that the adsorption of transition metal atoms on graphene induces the opening of a gap in the transmission function in one spin channel only. Charge carriers flowing through the nanojunction in Ti@graphene belong almost entirely to the minority spin component, and the spin polarization of the current is almost 100%. The opposite is found in Co@graphene, where the charge carriers belonging to the majority spin component are dominant. The analysis of the non equilibrium electron density distribution indicates that a spin separation between the left and the right portions of the device occurs. This strong spin asymmetry suggests that transition metal adatoms have the potential of turning graphene into an efficient spin-filtering device.