Mn dimers on graphene nanoribbons: An ab initio study

We show, using ab initio density functional theory calculations, that Mn dimers adsorbed on graphene nanoribbons (Mn2/GNRs) present a magnetic bistability, as does the isolated Mn dimer. Our total energy results indicate that Mn dimers lying along the edge sites of zigzag GNRs represent the most likely configuration. We find that similar to the isolated Mn2 molecule, the antiferromagnetic coupling represents the ground state for Mn2/GNR, and the spin density configuration of the GNR does not play an important role on the net magnetic moment of Mn2, which makes GNRs an ideal substrate for adsorption of these molecules. The ground state and the excited state configuration of the Mn dimer, viz., low-spin (LS) and high-spin (HS), are maintained in the face of changes in the spin density configuration of the substrate. Here we find that the Mn2/GNR systems exhibit a LS ↔ HS binary behavior, which can be considered as a useful property in the development of nanomemories based upon metallic clusters.