# Coherent long-range transfer of angular momentum between magnon Kittel modes by phonons

## TL;DR

This paper demonstrates the coherent transfer of angular momentum between distant magnon modes in magnetic bilayers via phonons, revealing a new mechanism for long-range magnon coupling mediated by sound waves.

## Contribution

It introduces a method for long-range, coherent angular momentum transfer between magnon modes using phonons in a magnetic bilayer system.

## Key findings

- Observation of ferromagnetic resonance in YIG bilayers.
- Interference pattern explained by strong magnon-phonon coupling.
- Potential for phonon-mediated angular momentum transfer in info tech.

## Abstract

We report ferromagnetic resonance in the normal configuration of an electrically insulating magnetic bilayer consisting of two yttrium iron garnet (YIG) films epitaxially grown on both sides of a 0.5-mm-thick nonmagnetic gadolinium gallium garnet (GGG) slab. An interference pattern is observed and it is explained as the strong coupling of the magnetization dynamics of the two YIG layers either in phase or out of phase by the standing transverse sound waves, which are excited through a magnetoelastic interaction. This coherent mediation of angular momentum by circularly polarized phonons through a nonmagnetic material over macroscopic distances can be useful for future information technologies.