  Organic and carbon-based materials are attractive for spintronics because
their small spin-orbit coupling and low hyperfine interaction is expected to
give rise to large spin-relaxation times. However, the corresponding
spin-relaxation length is not necessarily large when transport is via weakly
interacting molecular orbitals. Here we use graphite as a model system and
study spin transport in the direction perpendicular to the weakly bonded
graphene sheets. We achieve injection of highly (75%) spin-polarized electrons
into graphite nanostructures of 300-500 nm across and up to 17 nm thick, and
observe transport without any measurable loss of spin information. Direct
visualization of local spin transport in graphite-based spin-valve sandwiches
also shows spatially uniform and near-unity transmission for electrons at 1.8
eV above the Fermi level.
