Rashba-like spin textures in Graphene promoted by ferromagnet-mediated Electronic-Hybridization with heavy metal

Epitaxial graphene/ferromagnetic metal (Gr/FM) heterostructures deposited onto heavy metals (HM) have been proposed for the realization of novel spintronic devices because of their perpendicular magnetic anisotropy and sizeable Dzyaloshinskii-Moriya interaction (DMI), allowing for both enhanced thermal stability and stabilization of chiral spin textures. However, establishing routes towards this goal requires the fundamental understanding of the microscopic origin of their unusual properties. Here, we elucidate the nature of the induced spin-orbit coupling (SOC) at Gr/Co interfaces on Ir. Through spin- and angle-resolved photoemission along with density functional theory, we show that the interaction of the HM with the C atomic layer via hybridization with the FM is the source of strong SOC in the Gr layer. Furthermore, our studies on ultrathin Co films underneath Gr reveal an energy splitting of $\sim$\,100 meV (negligible) for in-plane (out-of-plane) spin polarized Gr $\pi$ bands, consistent with a Rashba-SOC at the Gr/Co interface, which is either the fingerprint or the origin of the DMI. This mechanism vanishes at large Co thicknesses, where neither in-plane nor out-of-plane spin-orbit splitting is observed, indicating that Gr $\pi$ states are electronically decoupled from the HM. The present findings are important for future applications of Gr-based heterostructures in spintronic devices.