Resonant properties of dipole skyrmions in amorphous Fe/Gd multilayers

TL;DR

This study investigates the resonant properties of dipole skyrmions in Fe/Gd multilayers through experiments and simulations, revealing localized spin-wave modes dependent on skyrmion helicity and distinguishing them from bubble domains.

Contribution

It provides the first detailed analysis of the dynamic resonant modes of dipole skyrmions in amorphous multilayers, combining experimental measurements with micromagnetic modeling.

Findings

Identification of four localized spin wave excitations in dipole skyrmions.

Resonant modes depend on skyrmion helicity and magnetic field conditions.

Dipole skyrmions exhibit distinct localized modes compared to bubble domains.

Abstract

The dynamic response of dipole skyrmions in Fe/Gd multilayer films is investigated by ferromagnetic resonance measurements and compared to micromagnetic simulations. We detail thickness and temperature dependent studies of the observed modes as well as the effects of magnetic field history on the resonant spectra. Correlation between the modes and the magnetic phase maps constructed from real-space imaging and scattering patterns allows us to conclude the resonant modes arise from local topological features such as dipole skyrmions but does not depend on the collective response of a closed packed lattice of these chiral textures. Using, micromagnetic modeling, we are able to quantitatively reproduce our experimental observations which suggests the existence of localized spin-wave modes that are dependent on the helicity of the dipole skyrmion. We identify four localized spin wave excitations for the skyrmions that are excited under either in-plane or out-of-plane r.f. fields. Lastly we show that dipole skyrmions and non-chiral bubble domains exhibit qualitatively different localized spin wave modes.