Reliability of spin-to-charge conversion measurements in graphene-based lateral spin valves

TL;DR

This study investigates the reliability of spin-to-charge conversion measurements in graphene-based lateral spin valves, revealing that observed signals can be artefacts unrelated to true spin-to-charge conversion, thus informing better experimental design.

Contribution

The paper demonstrates that signals previously attributed to spin-to-charge conversion in graphene may be artefacts, emphasizing the need for careful analysis in future experiments.

Findings

Signals mimicking inverse Rashba-Edelstein effect are artefacts in pristine graphene.

Stray field-induced Hall effects can explain these artefacts.

Finite-element simulations support the explanation of artefacts.

Abstract

Understanding spin physics in graphene is crucial for developing future two-dimensional spintronic devices. Recent studies show that efficient spin-to-charge conversions via either the inverse spin Hall effect or the inverse Rashba-Edelstein effect can be achieved in graphene by proximity with an adjacent spin-orbit coupling material. Lateral spin valve devices, made up of a graphene Hall bar and ferromagnets, are best suited for such studies. Here, we report that signals mimicking the inverse Rashba-Edelstein effect can be measured in pristine graphene possessing negligible spin-orbit coupling, confirming that these signals are unrelated to spin-to-charge conversion. We identify either the anomalous Hall effect in the ferromagnet or the ordinary Hall effect in graphene induced by stray fields as the possible sources of this artefact. By quantitatively comparing these options with finite-element-method simulations, we conclude the latter better explains our results. Our study deepens the understanding of spin-to-charge conversion measurement schemes in graphene, which should be taken into account when designing future experiments.