Skyrmion-(non)crystal structure stabilized by dipolar interaction

摘要

We report a numerical study on the role of longrange dipolar interaction played on the creation and stabilization of skyrmion-(non)crystal structure in chiral ferromagnetic thin films without any anisotropies,based on a Monte-Carlo simulation method.With the increase of external magnetic field,the microscopic spin configuration is transformed from a spin-spiral stripe or labyrinth structure,depending on the strength of dipolar interaction,into a skyrmion-(non)crystal structure,and then into a skyrmiongas structure,and finally into a ferromagnetic state.Interestingly,with the increase of dipolar interaction,the skyrmion-crystal structure evolves from a triangular arrangement into a square arrangement with the change of skyrmion shape from circle to square.For larger dipolar interactions,the skyrmion-crystal structure loses the regular arrangements and the skyrmions,remaining topological,exhibit different shapes and sizes and squeeze with each other,whose distributions are analogous to a non-crystal structure.Therefore,different skyrmion-(non)crystal structures are stabilized in different ranges of dipolar interactions,which further promotes the applications of skyrmions as non-volatile information carriers.