Chiral coupling-induced asymmetric domain wall motion

The engineering of chiral coupling in thin magnetic films with inhomogeneous anisotropy [1] allows for designing synthetic magnetic systems of fundamental and technological interest [2,3]. This coupling arises from the interfacial Dzyaloshinskii-Moriya interaction, which, in combination with spin-orbit torques, leads to the local manipulation of chiral magnetic order [4]. So far, the chiral coupling between nanomagnets with patterned magnetic anisotropy has been studied only in Pt/Co/AlOx trilayers.

Here we design a system for quantifying the chiral coupling based on field- and current-induced asymmetric domain wall motion in Pt/Co/AlOx racetracks. This establishes a versatile method to characterize the chiral coupling in different materials. We further provide evidence of chiral coupling in Pt/CoB/AlOx trilayers with ultralow pinning. We show that the domain walls in such a system propagate in response to the DMI effective field even in the absence of any external driving force. This work shows that the chiral coupling can be used to locally design intrinsic fields that affect the magnetization dynamics.

[1] Luo, et al. Science 363, 1435 (2019)
[2] Luo, et al. Nature 579, 214 (2020)
[3] Dao et al. Nano Lett. 19, 5930 (2019)
[4] Hrabec, et al. Appl. Phys. Lett. 117, 130503 (2020)