  This study theoretically investigated the magnetic properties and electronic
structure of a graphene-based nano-spin-valve-like structure. Magnetic nickel
layers on both sides of the graphene were considered. A spin-polarized
generalized-gradient approximation determined the electronic states. In an
energetically stable stacking arrangement of graphene and two nickel layers,
the anti-parallel spin configuration of the underlayer and overlayer magnetic
moments had the lowest energy, which is in agreement with previous experimental
studies. The spin density mapping and obtained band-structure results show that
when the upper and lower Ni(111) slabs have an anti-parallel (parallel)
magnetic-moment configuration, the carbon atoms of sublattices A and B will
have an antiferromagnetic (ferromagnetic) spin configuration. A band gap at the
Dirac cone was open when the alignment had an anti-parallel configuration and
closed when the alignment had a parallel configuration. Therefore, the in-plane
conductance of the graphene layer depends on the magnetic alignment of the two
nickel slabs when the Fermi level is adjusted at the Dirac point. Both the
magnetic properties and electronic structures of the Ni/graphene/Ni
nanostructure cause the system to be a new prospective spintronic device
showing controllable in-plane magnetoresistance.
