Structure and Electronic and Transport Properties of Transition Metal Intercalated Graphene and Graphene-Hexagonal-Boron-Nitride Bilayer

Structural, electronic, and magnetic properties of the Fe-, Co-, Ni-, and V-intercalated graphene bilayer sandwich (denoted by C-2 vertical bar M vertical bar C-2, M = Fe, Co, Ni, and V) and graphene on hexagonal boron nitride (h-BN) bilayer sandwich (denoted by C-2 vertical bar M vertical bar BN, M = Fe, Co, Ni, and V) are studied by using density functional theory method. We find that both the graphene bilayer and graphene-h-BN bilayer in all the C-2 vertical bar M vertical bar C-2 and C-2 vertical bar M vertical bar BN sandwiches favor AB stacking over AA stacking mode. The Fe, Co, and Ni atoms prefer to be located over the center of C-C bonds whereas V atoms prefer to be located above the C atoms on graphene, and they all prefer to be located above the N atoms on h-BN sheet, regardless of the stacking mode. The C-2 vertical bar Fe vertical bar C-2, C-2 vertical bar CO vertical bar C-2, C-2 vertical bar Fe vertical bar BN, and C-2 vertical bar Co vertical bar BN sandwiches of AB stacking are all ferromagnetic metals with the spin polarization of 86%, 67%, 65%, and 46% at the Fermi level, respectively. By contrast, both C-2 vertical bar Ni vertical bar C-2 and C-2 vertical bar Ni vertical bar BN sandwiches of AB stacking are nonmagnetic semiconductors with bandgaps of 0.64 and 0.23 eV, respectively, which provide a novel strategy of opening a bandgap of graphene. From the quantum transport calculation, we obtain a giant room-temperature magnetoresistance of similar to 200% in the spin valve device based on AB stacking C-2 vertical bar Fe vertical bar C-2 sandwich.