  Chiral magnetic materials provide a number of challenging issues such as the
highly efficient domain wall (DW) and skyrmion motions driven by electric
current, as of the operation principles of emerging spintronic devices. The DWs
in the chiral materials exhibit asymmetric DW speed variation under application
of in plane magnetic field. Here, we show that such DW speed asymmetry causes
the DW tilting during the motion along wire structure. It has been known that
the DW tilting can be induced by the direct Zeeman interaction of the DW
magnetization under application of in plane magnetic field. However, our
experimental observations manifests that there exists another dominant process
with the DW speed asymmetry caused by either the Dzyaloshinskii Moriya
interaction (DMI) or the chirality dependent DW speed variation. A theoretical
model based on the DW geometry reveals that the DW tilting is initiated by the
DW pinning at wire edges and then, the direction of the DW tilting is
determined by the DW speed asymmetry, as confirmed by a numerical simulation.
The present observation reveals the decisive role of the DW pinning with the DW
speed asymmetry, which determines the DW geometry and consequently, the
dynamics.
