  The in-plane lattice constants of close-packed planes of fcc and hcp Ni and
Co match that of graphite almost perfectly so that they share a common two
dimensional reciprocal space. Their electronic structures are such that they
overlap in this reciprocal space for one spin direction only allowing us to
predict perfect spin filtering for interfaces between graphite and (111) fcc or
(0001) hcp Ni or Co. First-principles calculations of the scattering matrix
show that the spin filtering is quite insensitive to amounts of interface
roughness and disorder which drastically influence the spin-filtering
properties of conventional magnetic tunnel junctions or interfaces between
transition metals and semiconductors. When a single graphene sheet is adsorbed
on these open $d$-shell transition metal surfaces, its characteristic
electronic structure, with topological singularities at the K points in the two
dimensional Brillouin zone, is destroyed by the chemical bonding. Because
graphene bonds only weakly to Cu which has no states at the Fermi energy at the
K point for either spin, the electronic structure of graphene can be restored
by dusting Ni or Co with one or a few monolayers of Cu while still preserving
the ideal spin injection property.
