# Bias induced up to 100% spin-injection and detection polarizations in ferromagnet/bilayer-hBN/graphene/hBN heterostructures

## TL;DR

This study demonstrates that bilayer-hBN tunnel barriers can induce extremely high and bias-dependent spin polarizations in graphene heterostructures at room temperature, significantly advancing practical spintronic device capabilities.

## Contribution

The paper reports the first observation of bias-induced large spin polarizations up to 135% in graphene with bilayer-hBN barriers, showing potential for improved spintronic applications.

## Key findings

- Record two-terminal spin signals up to 800 Ω
- Bias-induced spin polarizations up to 135%
- Spin accumulations up to 4.1 meV

## Abstract

We study spin transport in a fully hBN encapsulated monolayer-graphene van der Waals (vdW) 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 $\Omega$ with a magnetoresistance ratio of 2.7%, and we 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.