Magnetic vortex core reversal by excitation of spin waves

TLDR

Micron‑sized magnetic platelets in a flux‑closed vortex state possess a curling in‑plane magnetization and a nanometer‑sized perpendicular core, and their simple yet rich dynamics—low‑field gyrotropic core toggling and high‑frequency spin‑wave modes—make them a key system for micromagnetics and spintronics research. We experimentally show that exciting azimuthal spin‑wave modes induces a unidirectional vortex core reversal, a result confirmed by micromagnetic simulations that reveal selection rules and indicate the critical‑velocity switching criterion must be revised for spin‑wave excitation.

Abstract

Micron-sized magnetic platelets in the flux-closed vortex state are characterized by an in-plane curling magnetization and a nanometer-sized perpendicularly magnetized vortex core. Having the simplest non-trivial configuration, these objects are of general interest to micromagnetics and may offer new routes for spintronics applications. Essential progress in the understanding of nonlinear vortex dynamics was achieved when low-field core toggling by excitation of the gyrotropic eigenmode at sub-GHz frequencies was established. At frequencies more than an order of magnitude higher vortex state structures possess spin wave eigenmodes arising from the magneto-static interaction. Here we demonstrate experimentally that the unidirectional vortex core reversal process also occurs when such azimuthal modes are excited. These results are confirmed by micromagnetic simulations, which clearly show the selection rules for this novel reversal mechanism. Our analysis reveals that for spin-wave excitation the concept of a critical velocity as the switching condition has to be modified.