The magnetic domain wall is the boundary between two magnetic regions, or domains, within a magnetic material, where the magnetic moments in each domain are aligned in different directions. The phenomenon of current-induced domain wall motion is crucial for understanding how electric currents can manipulate the behavior of magnetic materials. In 2008, Parkin et al. proposed a shift-register model for data storage known as “domain-wall racetrack memory,” where the magnetization of a domain encodes a bit, and the position of the domain can be controlled by applying current pulses. This concept has become a vital area of research for developing advanced memory devices, such as racetrack memory and magnetic logic devices.

In this project, our focus lies in current-driven domain wall motion via spin or orbital torque resulting from the spin Hall effect (SHE) or orbital Hall effect (OHE). By injecting spin into magnetic materials, an effective torque field can cause the expansion or shrinkage of the domain wall. The presence of an in-plane field, which breaks the in-plane symmetry, assists this process, further leading the magnetization switching. However, for spin-torque-driven domain wall motion, the interfacial Dzyaloshinskii-Moriya interaction (DMI) is considered crucial for the formation of a Neel-type domain wall.

In the case of generating orbital currents in light metal systems, the interfacial DMI tends to be weak due to a weaker spin-orbit coupling, which in turn requires a weaker in-plane assist field to efficiently drive domain wall motion. Notably, the orbital Hall conductivity can be one order of magnitude stronger than the spin Hall conductivity, which indicates the orbital torque-driven domain wall motion could potentially require a significantly lower critical current. This phenomenon holds great promise for applications in next-generation memory and logic devices, particularly in racetrack memory and spin-orbitronic circuits.