Chirality-induced antisymmetry in magnetic domain wall speed

In chiral magnetic materials, numerous intriguing phenomena such as built-in chiral magnetic domain walls (DWs) and skyrmions are generated by the Dzyaloshinskii–Moriya interaction (DMI). The DMI also results in asymmetric DW speeds under an in-plane magnetic field, which provides a useful scheme to measure the strength of the DMI. However, recent findings of additional asymmetries such as chiral damping have inhibited the unambiguous determination of the DMI strength, and the underlying mechanism of overall asymmetries comes under debate. Here, we experimentally investigate the nature of the additional asymmetry by extracting the DMI-induced symmetric contribution from the DW speed. Our results reveal that the additional asymmetry has a truly antisymmetric nature with the typical behavior governed by the DW chirality. In addition, the antisymmetric contribution alters the DW speed by a factor of 100, dominating the overall variation in DW speed. Thus, experimental inaccuracies can be largely removed by calibration with such antisymmetric contributions, enabling the standard DMI measurement scheme. Fast-moving domain walls separating regions with spin-up or spin-down states are desirable for high-performance spintronic memory and logic devices. The Dzyaloshinskii–Moriya interaction gives rise to an asymmetric distribution of domain wall speeds in chiral magnetic materials, providing a convenient way to determine the strength of the interaction. However, the recent discovery of additional asymmetries has complicated the analysis of measurements. Now, Sug-Bong Choe from Seoul National University and co-workers have experimentally determined the chiral nature of the additional symmetry for the first time. This contribution, which could arise from either a form of energy dissipation called chiral damping or from natural variations in domain wall widths, can alter domain wall speeds by a factor of 100. Chiral magnetic domain-wall (DW) speed variation is investigated. We demonstrate that the symmetric contribution in the DW speed attributes to the chiral DW energy density. Next, by deducing this symmetric contribution, the additional asymmetry was extracted. The extracted additional asymmetry exhibits truly antisymmetric nature and is governed by DW chirality. Moreover, this antisymmetry (additional asymmetry) changes overall DW speed more than a factor of 100 to the extent of dominating the symmetric contribution. These findings not only provide the artifact-free Dyzaloshinskii–Moriya interaction measurement scheme, but also contribute to the investigation of the origin of the additional asymmetry.