Spin currents and magnetoresistance of graphene-based magnetic junctions

TL;DR

This paper investigates spin-dependent transport and magnetoresistance in graphene-based magnetic junctions using theoretical models, revealing geometry-dependent effects such as spin-valve behavior and negative differential resistance.

Contribution

It introduces a detailed theoretical analysis of how contact geometry influences spin transport and magnetoresistance in graphene magnetic junctions.

Findings

Zigzag interfaces exhibit high magnetoresistance ratios.

Negative differential resistance occurs for a single spin channel at positive gate voltage.

Armchair interfaces show linear I-V characteristics with low MR ratios.

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.