Flux-closure chirality control and domain wall trapping in asymmetric magnetic ring

Abstract

A technique for flux-closure chirality control and domain wall trapping at the narrowest position in asymmetric magnetic ring is proposed. Micromagnetic simulation work was performed on permalloy asymmetric magnetic rings to observe its magnetic switching behavior. By controlling the lateral geometric features, the ring asymmetry, and the thickness of the film, a local vortex-free reversal process and well-controlled chirality of flux closure can be achieved. Furthermore, a domain wall trapping feature is also observed at the narrow arm of the asymmetric ring, which corresponds to the phenomenon that the magnetic domain wall does not annihilate until the magnetization in the wide arm reversed in a relatively large magnetic field. A phase diagram of the asymmetric ring switching behavior shows that the switching regimes (e.g., the domain wall propagation or nucleation annihilation) of the asymmetric rings and the domain wall pinning depend mainly on the film thickness.