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Spin currents and magnetoresistance of graphene-based magnetic junctions
Using the tight-binding approximation and the nonequilibrium Green's function
approach, we investigate the coherent spin-dependent transport in planar
magnetic junctions consisting of two ferromagnetic (FM) electrodes separated by
a graphene flake (GF) with zigzag or armchair interfaces. It is found that the
electron conduction strongly depends on the geometry of contact between the GF
and the FM electrodes. In the case of zigzag interfaces, the junction
demonstrates a spin-valve effect with high magnetoresistance (MR) ratios and
shows negative differential resistance features for a single spin channel at
positive gate voltage. In the case of armchair interfaces, the current-voltage
characteristics behave linearly at low bias voltages and hence, both spin
channels are in on state with low MR ratios.Comment: 6 pages, 5 figure
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