▎ 摘　　要

The effects of the bias voltage placed on a second gate which is positioned to the left of the ferromagnetic graphene (FG) layer on the switching of the charge and spin transports in a ferromagnetic graphene junction are studied. We show that the change in the bias voltage from positive to negative (while maintaining the positive voltage on the first gate above the FG layer) can induce a switching from high to low conductance states in the junction. The voltage on the first gate is used to shift the Fermi level in the FG layer. Enhancement of the on/off conductance ratio on the switching is shown to be inversely proportional to the thickness of the second gate barrier. We show that by biasing the nanostructures with the voltage U(2), the spin polarization can be increased and that as a consequence, the thickness of the FG barrier layer needed for spin-polarized transport can be reduced. (C) 2009 Elsevier B.V. All rights reserved.