Realizing High-Quality Interfaces in Two-Dimensional Material Spin Valves

Two-dimensional (2D) materials are considered enabling components in magnetic spin valves that could increase the performance and robustness of spintronic devices. However, experimental results have been below expectations due to challenges in achieving contamination-free interfaces between the 2D material barrier and its ferromagnetic contacts. We demonstrate an approach to realize interfaces with unprecedented quality using a single-step fabrication approach. By simultaneously depositing two asymmetric contacts on a suspended 2D material, the effect of oxidation and voiding can be avoided. Graphene-based spin valves show a strong interaction at the interface that leads to exceptional magnetoresistance values. This advance permits the characterization of the intrinsic spin properties at the Co/graphene interface, and we establish the limitations of traditional Hanle-based spin-lifetime measurements. Finally, we investigate the differences in spin transport for multilayer graphene-based spin valves. An increased level of spin-scattering is observed that limits the achievable performance and provides guidelines for the future integration of 2D materials in spintronic devices.