# Non-reciprocity of spin waves in magnetic nanotubes with helical equilibrium magnetization

## TL;DR

This paper explores how magnetic nanotubes with helical magnetization exhibit tunable nonreciprocal spin wave behavior influenced by dipolar and exchange interactions, with potential applications in 3D magnonic devices.

## Contribution

It reveals that isotropic-exchange interactions can induce chiral effects in spin wave transport and demonstrates tunability between dipolar and exchange regimes in helical states.

## Key findings

- Nonreciprocal spin wave dispersion can be tuned via magnetic fields.
- Exchange interactions can induce chiral effects similar to dipolar interactions.
- A device proposal for measuring exchange and dipole-induced nonreciprocities.

## Abstract

Spin waves (SWs) in magnetic nanotubes have shown interesting nonreciprocal properties in their dispersion relation, group velocity, frequency linewidth and attenuation lengths. The reported chiral effects are similar to those induced by the Dzyaloshinskii-Moriya interaction, but originating from the dipole-dipole interaction. Here we show, that the isotropic-exchange interaction can also induce chiral effects in the SW transport; the so-called Berry phase of SWs. We demonstrate that with the application of magnetic fields, the nonreciprocity of the different SW modes can be tuned between the fully dipolar governed and the fully exchange governed cases, as they are directly related to the underlaying equilibrium state. In the helical state, due to the combined action of the two effects every single sign combination of the azimuthal and axial wave vectors leads to different dispersion, allowing for a very sophisticated tuning of the SW transport. A disentanglement of the dipole-dipole and exchange contributions so far was not reported for the SW transport in nanotubes. Furthermore, we propose a device based on coplanar waveguides that would allow to selectively measure the exchange or dipole induced SW nonreciprocities. In the context of magnonic applications, our results might encourage further developments in the emerging field of 3D magnonic devices using curved magnetic membranes.