Spin lifetimes exceeding 12 nanoseconds in graphene non-local spin valve devices

TL;DR

This study demonstrates record-long spin lifetimes exceeding 12 nanoseconds in graphene non-local spin valve devices at room temperature, achieved through advanced fabrication techniques that mitigate contact effects.

Contribution

The paper reports the first observation of spin lifetimes over 12 ns in graphene devices at room temperature, surpassing previous records and challenging existing models of contact-induced spin relaxation.

Findings

Spin lifetimes of 12.6 ns achieved at room temperature

Spin diffusion lengths as long as 30.5 μm observed

Long spin lifetimes despite presence of conducting pinholes

Abstract

We show spin lifetimes of 12.6 ns and spin diffusion lengths as long as 30.5 \mu m in single layer graphene non-local spin transport devices at room temperature. This is accomplished by the fabrication of Co/MgO-electrodes on a Si/SiO$_2$ substrate and the subsequent dry transfer of a graphene-hBN-stack on top of this electrode structure where a large hBN flake is needed in order to diminish the ingress of solvents along the hBN-to-substrate interface. Interestingly, long spin lifetimes are observed despite the fact that both conductive scanning force microscopy and contact resistance measurements reveal the existence of conducting pinholes throughout the MgO spin injection/detection barriers. The observed enhancement of the spin lifetime in single layer graphene by a factor of 6 compared to previous devices exceeds current models of contact-induced spin relaxation which paves the way towards probing intrinsic spin properties of graphene.