The anatomy of magnetic field pulse induced transverse domain wall dynamics

The microscopic anatomy of the precessional torque-induced magnetic domain wall racetrack memory is numerically investigated. A systematic analysis is performed to explain the efficiency and limitations of this domain wall motion architecture. A transverse domain wall in an in-plane magnetic nanowire is chosen, and the direction of the applied magnetic field is applied to be perpendicular to the film plane. The domain wall displacement upon the application of an out-of-plane magnetic field pulses is shown to be driven by the precessional torque and subsequently decelerated by the damping torque, causing the domain wall to settle at a specific position. Crucially, a characteristic frequency is exhibited by this domain wall dynamics. After removing the magnetic field, a reverse domain wall dynamics is observed with the same frequency, causing the domain wall to revert to its original position. To realize continuous domain wall motion, a notch structure is introduced, and the depinning field is calculated as a function of the out-of-plane field strength. The analysis reveals that the depinning field decreases linearly as the out-of-plane field strength increases. Finally, the principle of domain wall hopping in a multiple-notched nanowire is verified by the application of sequential out-of-plane field pulses.