Abstract

We study spin transport in a fully hBN encapsulated monolayer-graphene van der Waals heterostructure at room temperature. A top-layer of bilayer-hBN is used as a tunnel barrier for spin-injection and detection in graphene with ferromagnetic cobalt electrodes. We report surprisingly large and bias-induced (differential) spin-injection (detection) polarizations up to 50% (135%) at a positive voltage bias of + 0.6 V, as well as sign inverted polarizations up to −70% (−60%) at a reverse bias of −0.4 V. This demonstrates the potential of bilayer-hBN tunnel barriers for practical graphene spintronics applications. With such enhanced spin-injection and detection polarizations, we report a record two-terminal (inverted) spin-valve signals up to 800 Ω with a magnetoresistance ratio of 2.7%, and achieve spin accumulations up to 4.1 meV. We propose how these numbers can be increased further, for future technologically relevant graphene based spintronic devices.

Highlights

  • We study spin transport in a fully hexagonal boron nitride (hBN) encapsulated monolayer-graphene van der Waals heterostructure at room temperature

  • In order to explore the potential of hBN tunnel barriers for graphene spin valve devices, one can study the role of current/ voltage bias for spin-injection and detection with FM electrodes

  • Recent first-principles calculations of the proximity exchange coupling induced in graphene by Zollner et al.[12] have predicted that an applied electric field in Co/hBN/graphene system can reverse the sign of the proximity-effect-induced equilibrium spin polarization in graphene

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Summary

Introduction

We study spin transport in a fully hBN encapsulated monolayer-graphene van der Waals heterostructure at room temperature. We report surprisingly large and bias-induced (differential) spin-injection (detection) polarizations up to 50% (135%) at a positive voltage bias of + 0.6 V, as well as sign inverted polarizations up to −70% (−60%) at a reverse bias of −0.4 V This demonstrates the potential of bilayer-hBN tunnel barriers for practical graphene spintronics applications. With such enhanced spininjection and detection polarizations, we report a record two-terminal (inverted) spin-valve signals up to 800 Ω with a magnetoresistance ratio of 2.7%, and achieve spin accumulations up to 4.1 meV. We propose how these numbers can be increased further, for future technologically relevant graphene based spintronic devices. We demonstrate a two-terminal (inverted) spin-valve with a record magnitude of the spin signal reaching 800 Ω with magnetoresistance ratio of 2.7%

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