  Employing Brillouin spectroscopy, strong interfacial Dzyaloshinskii-Moriya
interactions have been observed in an ultrathin Pt/CoFeB film. Our
micromagnetic simulations show that spin-wave nonreciprocity due to asymmetric
surface pinning is insignificant for the 0.8nmthick CoFeB film studied. The
observed high asymmetry of the monotonic spin wave dispersion relation is thus
ascribed to strong Dzyaloshinskii-Moriya interactions present at the Pt/CoFeB
interface. Our findings should further enhance the significance of CoFeB as an
important material for magnonic, spintronic and skyrmionic applications.
