  Graphene/ferromagnet interface promises a plethora of new science and
technology. The interfacial Dzyaloshinskii Moriya interaction (iDMI) is
essential for stabilizing chiral spin textures, which are important for future
spintronic devices. Here, we report direct observation of iDMI in
graphene/Ni80Fe20/Ta heterostructure from non-reciprocity in spin-wave
dispersion using Brillouin light scattering (BLS) technique. Linear scaling of
iDMI with the inverse of Ni80Fe20 thicknesses suggests primarily interfacial
origin of iDMI. Both iDMI and spin-mixing conductance increase with the
increase in defect density of graphene obtained by varying argon pressure
during sputter deposition of Ni80Fe20. This suggests that the observed iDMI
originates from defect-induced extrinsic spin-orbit coupling at the interface.
The direct observation of iDMI at graphene/ferromagnet interface without
perpendicular magnetic anisotropy opens new route in designing thin film
heterostructures based on 2-D materials for controlling chiral spin structure
such as skyrmions and bubbles, and magnetic domain-wall-based storage and
memory devices.
