Massive Dirac fermion transport in a gapped graphene-based magnetic tunnel junction

The spin transport in a graphene-based magnetic (NG/ferromagnetic barrier (FB)/NG) tunnel junction with the graphene sheet being grown on a SiC substrate is investigated. Zhou et al. [Nat. Mater. 6 (2007) 770] has shown that in these epitaxial grown graphene sheets, the electrons behave like massive relativistic particles with an energy gap of 2 Delta similar to 260 meV opening up in the energy spectrum of the massive relativistic electron. Basing on assumption that gap in graphene can occur under the influence of the magnetic field, we find that in the case of thick ferromagnetic graphene barriers, the electronic gap causes the barrier to behave as a strong insulator when the gate potential is in the range 400-130 meV<400+130 meV (and the energy level E-f similar to 400 meV above Dirac point). For these values of V-G, the spin polarization of the junction is P(%)similar to 100% except for V-G = E-f, where it is P(%) = 0%. The current of the junction, for thick FB, can be rapidly switched from a 100% spin up current to a 100% spin down current by small variation of V-G from V-G < E-f to V-G > E-f, the features of a perfect spin filtering electronic junction. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.