Enhancement of Spin Transport Properties in Angled-Channel Graphene Spin Valves via Hybrid Spin Drift-Diffusion

Graphene has promise as a channel connecting separate units of large-scale spintronic circuits owing to its outstanding theoretical spin transport properties. However, spin transport properties of experimental devices consistently fall short of theoretical estimates due to impacts from the substrate, electrodes, or defects in the graphene itself. In this study, we fabricate both traditional non-local spin valves (NLSVs) and novel hybrid drift-diffusion spin valves (HDDSVs) to explore the impact of charge current and AC spin injection efficiency on spin transport. HDDSVs feature channel branches that allow investigation of charge-based spin drift enhancement compared to diffusion-only configurations. We investigate the modulation of spin transport through hybrid drift-diffusion, observing a decrease in spin signal by 11% for channels with a 45° branch angle, and a 21% increase in spin signal for 135° branch angle channels. We then fabricate symmetrical 90° channel branch angle devices, which do not produce consistent spin transport modulation in drift diffusion mode. These findings highlight the role of carrier drift in enhancing or suppressing spin transport, depending on channel geometry and injection configuration. Overall, our work demonstrates a promising approach to optimizing spin transport in graphene devices by leveraging hybrid drift-diffusion effects without requiring additional DC current sources.