Spin field-effect transistor action via tunable polarization of the spin injection in a Co/MgO/graphene contact

TL;DR

This paper demonstrates a spin field-effect transistor using a Co/MgO/graphene contact where the spin polarization can be electrically tuned and inverted, enabling control of spin injection via gate voltage and bias.

Contribution

It introduces a tunable spin injection mechanism in a graphene-based device, combining experimental fabrication with a theoretical model explaining the bias and gate dependence.

Findings

Spin polarization can be turned off and inverted by bias and gate voltage.

The device functions as a spin transistor controlled by electric fields.

A model explains the shift in the density of states affecting spin injection.

Abstract

We fabricated a non-local spin valve device with Co-MgO injector/detector tunnel contacts on a graphene spin channel. In this device, the spin polarization of the injector contact can be tuned by both the injector current bias and the gate voltage. The spin polarization can be turned off and even inverted. This behavior enables a spin transistor where the signal is switched off by turning off the spin injection using the field-effect. We propose a model based on a gate-dependent shift of the minimum in the graphene density of states with respect to the tunneling density of states of cobalt, which can explain the observed bias and gate dependence.