Voltage-controlled inversion of tunnel magnetoresistance in epitaxial Nickel/Graphene/MgO/Cobalt junctions

TL;DR

This paper demonstrates voltage-controlled inversion of tunnel magnetoresistance in epitaxial Nickel/Graphene/MgO/Cobalt junctions, revealing bias-dependent sign changes explained by phonon-assisted transport at the hybrid interface.

Contribution

It introduces a novel spin-valve structure with voltage-tunable TMR sign changes, explained by a new phonon-assisted transport model at the graphene|Ni interface.

Findings

Robust, scalable TMR with sign reversal upon bias variation

Phonon-assisted transport explains TMR sign changes

Hybrid graphene|Ni interface influences spin transport

Abstract

We report on the fabrication and characterization of vertical spin-valve structures using a thick epitaxial MgO barrier as spacer layer and a graphene-passivated Ni film as bottom ferromagnetic electrode. The devices show robust and scalable tunnel magnetoresistance, with several changes of sign upon varying the applied bias voltage. These findings are explained by a model of phonon-assisted transport mechanisms that relies on the peculiarity of the band structure and spin density of states at the hybrid graphene|Ni interface.