Eur. Phys. J. B 67, 239-244 (2009)
https://doi.org/10.1140/epjb/e2009-00034-6

Spin currents and magnetoresistance of graphene-based magnetic junctions

¹ Department of Physics, Payame Noor University, Nejatollahi Street, 159995-7613, Tehran, Iran
² Computational Physical Sciences Laboratory, Department of Nano-Science, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395, Tehran, Iran
³ Department of Physics, Islamic Azad University, North Tehran Branch, Darband Street, Tehran, Iran

Corresponding author: ^a a-saffar@tehran.pnu.ac.ir

Received: 22 October 2008
Revised: 22 December 2008
Published online: 4 February 2009

Abstract

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.