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

Abstract

We show that the ${d}^{0}$ ferromagnetism with high Curie temperature $({T}_{c})$ 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 ${T}_{c}$ 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.