Repeated deterministic defect-assisted switching of magnetic vortex core polarity

TL;DR

This paper demonstrates controlled, repeated switching of magnetic vortex core polarity at significantly reduced critical velocities by locally inducing defects, advancing magnetic data storage technology.

Contribution

It introduces a method to reduce the critical velocity for vortex core switching through defect engineering, enabling deterministic and repeated polarity reversal.

Findings

Repeated vortex core reversal at velocities as low as 20 m/s.

Defect creation via laser reduces exchange coupling locally.

Micromagnetic simulations confirm defect-induced switching sites.

Abstract

Because of its stability, the polarity of a magnetic vortex core (VC) is a candidate for binary data storage. Switching can be accomplished, e.g, by driving the VC above a critical velocity $v_c$. Here, we report on controlled and repeated switching of VC polarity by significantly reducing $v_c$ locally. We excite vortex dynamics in thin Permalloy disks with a magnetic field pulse, and map the two-dimensional VC trajectory using time-resolved Kerr microscopy. In pristine samples, we observe normal gyrotropic motion of the VC. After laser-induced generation of defects, however, we observe repeated VC reversal at much-reduced critical velocities as low as 20 m/s. Micromagnetic simulations reveal how local reduction of exchange coupling can create VC reversal sites for deterministic VC switching.