Observation of non-linear magnetic vortex gyration by X-ray microscopy and micromagnetic simulations

TL;DR

This study combines X-ray microscopy and simulations to observe non-linear magnetic vortex gyration in Permalloy squares, revealing a frequency redshift with increased excitation amplitude, advancing understanding of vortex dynamics.

Contribution

It provides the first direct experimental observation of non-linear vortex gyration in thicker nanostructures, confirming simulation predictions and contrasting previous findings.

Findings

Non-linear vortex behavior with a redshift in resonance frequency.

Agreement between experimental observations and micromagnetic simulations.

Contrast with earlier studies showing a blueshift in thinner structures.

Abstract

Magnetic vortex gyration in a 500 nm wide, 50 nm thick Permalloy square platelet was investigated using time-resolved scanning transmission x-ray microscopy and micromagnetic simulations. The response of the vortex core on an in-plane oscillating magnetic field was studied as a function of the excitation frequency and amplitude. Non-linear behavior was observed in the form of a redshift of the gyrotropic resonance. I.e., when the excitation amplitude was increased, the resonance frequency was found to decrease. The nonlinearity is in agreement with extensive micromagnetic simulations. This work complements previous reports on thinner nanostructures where a frequency blueshift was observed.