Spin precession and spin Hall effect in monolayer graphene/Pt nanostructures

TL;DR

This paper reports a significant enhancement of spin Hall signals in monolayer graphene/Pt devices, enabling detailed spin precession studies and accurate measurement of spin relaxation times, advancing spintronics technology.

Contribution

It introduces a two-order magnitude signal enhancement in graphene/Pt devices and develops an analytical model for determining spin relaxation times via the spin Hall effect.

Findings

Enhanced spin Hall signals by 100 times in graphene/Pt devices

Observed 100% spin absorption in platinum

Measured large effective spin Hall angle of up to 0.15

Abstract

Spin Hall effects have surged as promising phenomena for spin logics operations without ferromagnets. However, the magnitude of the detected electric signals at room temperature in metallic systems has been so far underwhelming. Here, we demonstrate a two-order of magnitude enhancement of the signal in monolayer graphene/Pt devices when compared to their fully metallic counterparts. The enhancement stems in part from efficient spin injection and the large resistivity of graphene but we also observe 100% spin absorption in Pt and find an unusually large effective spin Hall angle of up to 0.15. The large spin-to-charge conversion allows us to characterise spin precession in graphene under the presence of a magnetic field. Furthermore, by developing an analytical model based on the 1D diffusive spin-transport, we demonstrate that the effective spin-relaxation time in graphene can be accurately determined using the (inverse) spin Hall effect as a means of detection. This is a necessary step to gather full understanding of the consequences of spin absorption in spin Hall devices, which is known to suppress effective spin lifetimes in both metallic and graphene systems.