Current Induced Dynamics of Multiple Skyrmions with Domain Wall Pair and Skyrmion-based Majority Gate Design

As an intriguing ultra-small particle-like magnetic texture, skyrmion has attracted lots of research interests in next-generation ultra-dense and low power magnetic memory/logic designs. Previous studies have demonstrated a single skyrmion-domain wall pair collision in a specially designed magnetic racetrack junction. In this work, we investigate the dynamics of multiple skyrmions with domain wall pair in a magnetic racetrack. The numerical micromagnetic simulation results indicate that the domain wall pair could be pinned or depinned by the rectangular notch pinning site depending on both the number of skyrmions in the racetrack and the magnitude of driving current density. Such emergent dynamical property could be used to implement a threshold-tunable step function, in which the inputs are skyrmions and threshold could be tuned by the driving current density. The threshold-tunable step function is widely used in logic and neural network applications. We also present a three-input skyrmion-based majority logic gate design to demonstrate the potential application of such dynamic interaction of multiple skyrmions and domain wall pair.