Formation and annihilation of multi-antiskyrmion defects during skyrmion nucleation

Abstract

Magnetic skyrmions and antiskyrmions are intriguing topological defects in spin textures. A single-antiskyrmion defect would form and collapse to straightforwardly complete the topological transition for the nucleation of a skyrmion phase from a ferromagnetic background. Here, a novel multi-antiskyrmion defects-driven skyrmion nucleation mechanism is investigated in both the ferromagnetic single layer and synthetic antiferromagnetic trilayers with the spin-polarized current stimuli. The multi-antiskyrmion defects mechanism needs lower nucleation activation energy than the single-antiskyrmion defect mechanism and brings about intriguing fluctuations in topological charge. The multi-antiskyrmion defects mechanism can survive even at room temperature and is robust against simulation parameters. Our finding not only unravels an unprecedented skyrmion nucleation process but also provides a platform for investigating antiskyrmions as topological defects during topological transition.