  Magnetic racetrack memory has significantly evolved and developed since its
first experimental verification and is considered as one of the most promising
candidates for future high-density on-chip solid state memory. However, the
lack of a fast and precise magnetic domain wall (DW) shifting mechanism and the
required extremely high DW motion (DWM) driving current both make the racetrack
difficult to commercialize. Here, we propose a method for coherent DWM that is
free from above issues, which is driven by chirality switching (CS) and an
ultralow spin-orbit-torque (SOT) current. The CS, as the driving force of DWM,
is achieved by the sign change of DM interaction which is further induced by a
ferroelectric switching voltage. The SOT is used to break the symmetry when the
magnetic moment is rotated to the Bloch direction. We numerically investigate
the underlying principle and the effect of key parameters on the DWM through
micromagnetic simulations. Under the CS mechanism, a fast (102 m/s), ultralow
energy (5 attojoule), and precisely discretized DWM can be achieved.
Considering that skyrmions with topological protection and smaller size are
also promising for future racetrack, we similarly evaluate the feasibility of
applying such a CS mechanism to a skyrmion. However, we find that the CS only
causes it to "breathe" instead of moving. Our results demonstrate that the CS
strategy is suitable for future DW racetrack memory with ultralow power
consumption and discretized DWM.
