Tunable magnetic interaction in hydrogenated epitaxial graphene modulated by the SiC substrate

We show that the d0 ferromagnetism with high Curie temperature (Tc) can be achieved in the electron-doped hydrogenated epitaxial graphene on certain SiC substrates through first-principles calculations. The pristine systems are found to be Mott insulators regardless of SiC polytype (2H,4H, or 6H) which, however, plays a significant role in the modulation of magnetic interaction. Carrier doping enhances the ferromagnetic coupling due to the double-exchange mechanism and thus realizes the phase transition from antiferromagnetism to ferromagnetism. A Tc of around 400 K is predicted for graphene on the 2H-SiC substrate. We employ a nondegenerate Hubbard model to demonstrate how the SiC affects the interfacial magnetism in intra-atomic Coulomb repulsion and intersite hopping interactions.