Dynamic behavior of skyrmion collision: spiral and breath

A magnetic skyrmion is a particle-like topological soliton, which is an ideal candidate for developing high-density storage and logic devices due to its nonvolatility and tunability. In view of the particle motion characteristics of skyrmion, different skyrmions in a material inevitably interact in the form of short-range repulsion and long-range attraction. In this work, the dynamic characteristics of skyrmion collision in a ferromagnetic Co thin film are investigated by using micromagnetic simulations. It is found that the dynamic behavior of skyrmion after collision is highly dependent on the size of the strip, the initial velocity of skyrmion and magnetic damping constant. For the collision of two skyrmions, when the strip width exceeds the critical value, the skyrmions form a pair and rotate counterclockwise in the form of spiral and breath. It is interesting that the rotation and breath of skyrmions keep the same periodicity under the negligible damping, and the frequency increases with the increase of the initial velocity of skyrmion. Further, the collision of a system of three skyrmions reveals that they interact in pairs to form closed periodic trajectories. The results of the present work not only give an insight into the multi-skyrmion dynamics, but also provide guidance for the development of spintronic devices based on multi-skyrmion motion.