Determination of superexchange correlations in magnetically substituted graphene*

We investigate the electronic and magnetic properties between two homogeneous magnetic impurities (vanadium, chromium, or manganese) in a 128-atom graphene superlattice. With varying the impurity distance, we calculate these properties using a first principles approach. For each configuration, we determine the electronic bandstructure and density of states, along with the Mullikan populations for each atom. Furthermore, we calculate the exchange parameter between the two magnetic ions through the analysis of the change in total energy for different magnetic configurations. We found that the magnetic impurities induce a mangetic moment in the graphene superlattice, helping to meditate the superexchange between the impurities. Depending on the choice of ion used, the interactions between the two ions can exhibit either a ferromagnetic or an antiferromagnetic behavior. These correlations indicate an RKKY-like behavior in the system.