▎ 摘　　要

In the present letter, we report phenomena at the Co vertical bar Graphene vertical bar Co interfaces based on first principles calculations. The nature of Co-C-Co and Co-graphene-Co atomic bonding at the interfaces were investigated by means of density of states, electron and spin density analysis. We show that the spins are antiferromagnetic coupled across the interface via the pd-pi interactions between the Gr and Co layers, as exemplified by the superexchange mechanism. As a consequence, the spin injection efficiency at the Co vertical bar Graphene vertical bar Co interfaces and junctions will be reduced. (C) 2011 American Institute of Physics. [doi:10.1063/1.3571553]