Defect-Density- and Rashba-Shift-Induced Interfacial Dzyaloshinskii–Moriya Interaction and Spin Pumping in Single-Layer Graphene/Co₂₀Fe₆₀B₂₀ Heterostructures: Implications for New-Generation Spintronics

The quest for quantum phenomena in unconventional materials has led to the development of myriad unique systems. Because of their unusual atomic-scale interface properties and their controllability, graphene/ferromagnet heterostructures have emerged as a strong contender for next-generation spintronics. Further development demands superior properties and correlation between the different microscopic mechanisms involved. Herein, we demonstrate a superior interfacial Dzyaloshinskii–Moriya interaction (iDMI) in single-layer graphene/CoFeB/SiO2 heterostructures from asymmetric spin-wave dispersion measurement using a Brillouin light-scattering technique. The spin-wave frequencies and line widths have been correlated with structural and nanoscale morphological properties to evaluate the roles of Rashba shift and defect density for the emergence of iDMI and spin pumping for a range of thicknesses of the CoFeB layer, where the defects have been found to play a dominant role for the extrinsic spin–orbit coupling over the Rashba shift. A significantly large iDMI and spin-mixing conductance have been observed even at moderately low Ar pressure during sputter deposition of the ferromagnetic layer, which asserts further optimization of the said properties with external deposition parameters for application in next-generation energy-efficient and miniaturized spintronic and spin–orbitronic devices.