# Linearly polarized GHz magnetization dynamics of spin helix modes in the ferrimagnetic insulator Cu$_{2}$OSeO$_{3}$

## TL;DR

This paper demonstrates that the ferrimagnetic insulator Cu$_{2}$OSeO$_{3}$ exhibits linearly polarized magnetization dynamics at around 2 GHz, with polarization properties tunable by sample geometry, offering new insights for microwave technology applications.

## Contribution

It reveals that Cu$_{2}$OSeO$_{3}$ shows bulk linear dichroism in magnetization dynamics at GHz frequencies, a phenomenon not previously observed in such materials.

## Key findings

- Linearly polarized GHz magnetization dynamics observed in Cu$_{2}$OSeO$_{3}$
- Polarization plane switchable by slight changes in sample width
- Broad shape range supports linear polarization in bulk material

## Abstract

Linear dichroism -- the polarization dependent absorption of electromagnetic waves -- is routinely exploited in applications as diverse as structure determination of DNA or polarization filters in optical technologies. Here filamentary absorbers with a large length-to-width ratio are a prerequisite. For magnetization dynamics in the few GHz frequency regime strictly linear dichroism was not observed for more than eight decades. Here, we show that the bulk chiral magnet Cu$_{2}$OSeO$_{3}$ exhibits linearly polarized magnetization dynamics at an unexpectedly small frequency of about 2 GHz. Unlike optical filters that are assembled from filamentary absorbers, the magnet provides linear polarization as a bulk material for an extremely wide range of length-to-width ratios. In addition, the polarization plane of a given mode can be switched by 90$^\circ$ via a tiny variation in width. Our findings shed a new light on magnetization dynamics in that ferrimagnetic ordering combined with anisotropic exchange interaction offers strictly linear polarization and cross-polarized modes for a broad spectrum of sample shapes. The discovery allows for novel design rules and optimization of microwave-to-magnon transduction in emerging microwave technologies.