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We have characterized the strength of the interfacial Dyzaloshinskii-Moriya interaction (DMI) in ultrathin perpendicularly magnetized CoFeB/MgO films, grown on different underlayers of W, TaN, and Hf, using two experimental methods. First, we determined the effective DMI field from measurements of field-driven domain wall motion in the creep regime, where applied in-plane magnetic fields induce an anisotropy in the wall propagation that is correlated with the DMI strength. Second, Brillouin light spectroscopy was employed to quantify the frequency nonreciprocity of spin waves in the CoFeB layers, which yielded an independent measurement of the DMI. By combining these results, we show that DMI estimates from the different techniques yield only qualitative agreement, which suggests that open questions remain about the underlying models used to interpret these results. [ABSTRACT FROM AUTHOR]

The Dzyaloshinskii-Moriya interaction (DMI) has recently attracted considerable interest owing to its fundamental role in the stabilization of chiral spin textures in ultrathin ferromagnets, which are interesting candidates for future spintronic technologies. Here we employ a scanning nanomagnetometer based on a single nitrogen-vacancy defect in diamond to locally probe the strength of the interfacial DMI in CoFeB|MgO ultrathin films grown on different heavy metal underlayers X=Ta, TaN, and W. By measuring the stray field emanating from domain walls in micron-long wires of such materials, we observe deviations from the Bloch profile for TaN and W underlayers that are consistent with a positive DMI value favoring right-handed chiral spin structures. Moreover, our measurements suggest that the DMI constant might vary locally within a single sample, illustrating the importance of local probes for the study of magnetic order at the nanoscale. [ABSTRACT FROM AUTHOR]

The channeling of spin waves with domain walls in ultrathin ferromagnetic films is demonstrated theoretically and through micromagnetics simulations. It is shown that propagating excitations localized to the wall, which appear in the frequency gap of bulk spin wave modes, can be guided in curved geometries and propagate in close proximity to other channels. For Néel-type walls arising from a Dzyaloshinskii-Moriya interaction, the channeling is strongly nonreciprocal and group velocities can exceed 1  km/s in the long wavelength limit for certain propagation directions. The channeled modes represent an unusual analogy of whispering gallery waves that are one dimensional and nonreciprocal with this interaction. Moreover, a sufficiently strong Dzyaloshinskii-Moriya interaction can create a degeneracy of channeled and propagating modes at a critical wave vector.