Examination of the magnetic interactions between divacant Fe dimers in graphene

In this study, we investigate the isolated magnetic interactions between two identical Fe atoms substituted into graphene. Using density functional theory, we simulated a supercell of graphene with variably-spaced iron atoms in the divacant configuration and determined the electronic and magnetic properties for each system. Overall, we find that the exchange interaction between the two Fe atoms fluctuates between ferromagnetic and antiferromagnetic as the spatial distance in the zig-zag direction increases. Given the induced magnetic moment and increased density of states by the surrounding carbon atoms, it is clear that the exchange interactions undergo an RKKY-like interaction. Furthermore, we examined the same interactions for Fe atoms along the arm chair direction and find no evidence for an RKKY interaction, which indicates a directional dependent interaction within the graphene.