Spin wave localization and guiding by magnon band structure engineering in yttrium iron garnet

TL;DR

This paper demonstrates how engineering the magnon band structure in yttrium iron garnet enables localized control and guiding of spin waves, facilitating advanced magnonic device functionalities.

Contribution

It introduces a method to control spin-wave propagation and localization through band structure engineering and wave vector selectivity in yttrium iron garnet.

Findings

Wave vector selection suppresses dispersion effects.

Local engineering of dispersion enables magnonic waveguides.

Near an avoided crossing, group velocity approaches zero, enhancing control.

Abstract

In spintronics the propagation of spin-wave excitations in magnetically ordered materials can also be used to transport and process information. One of the most popular materials in this regard is the ferrimagnetic insulator yttrium-iron-garnet due its exceptionally small spin-wave damping parameter. While the small relaxation rate allows for large propagation length of magnetic excitations, it also leads to non-locality of the magnetic properties. By imaging spin waves their band structure is mapped. In doing so wave vector selection is shown to suppress dispersion effects to a large extent allowing for local measurements of spin relaxation. Moreover we demonstrate even higher control of magnon propagation by employing the wave vector selectivity near an avoided crossing of different spin-wave modes where the group velocity approaches zero. Here local engineering of the dispersion allows constructing magnonic waveguides and at the same time reveals the local relaxation properties.