Confined dipole and exchange spin waves in a bulk chiral magnet with Dzyaloshinskii-Moriya interaction

TL;DR

This study reveals the existence of confined dipole and exchange spin waves in bulk Cu$_2$OSeO$_3$, demonstrating Dzyaloshinskii-Moriya interaction's role in enabling exchange spin waves without nanofabrication.

Contribution

It provides experimental and micromagnetic evidence of high-order confined spin waves influenced by DMI in a bulk chiral magnet, expanding understanding of spin wave spectra.

Findings

Confined spin waves observed up to the 11th order.

Simultaneous excitation of dipole- and exchange-dominated spin waves.

Exchange spin waves with wavelengths around 47 nm identified.

Abstract

The Dzyaloshinskii-Moriya interaction (DMI) has an impact on excited spin waves in the chiral magnet Cu$_2$OSeO$_3$ by means of introducing asymmetry on their dispersion relations. The confined eigenmodes of a chiral magnet are hence no longer the conventional standing spin waves. Here we report a combined experimental and micromagnetic modeling study by broadband microwave spectroscopy we observe confined spin waves up to eleventh order in bulk Cu$_2$OSeO$_3$ in the field-polarized state. In micromagnetic simulations we find similarly rich spectra. They indicate the simultaneous excitation of both dipole- and exchange-dominated spin waves with wavelengths down to (47.2 $\pm$ 0.05) nm attributed to the exchange interaction modulation. Our results suggest DMI to be effective to create exchange spin waves in a bulk sample without the challenging nanofabrication and thereby to explore their scattering with noncollinear spin textures.