Phase-resolved imaging of coherent phonon-magnon coupling

TL;DR

This paper demonstrates phase-resolved optical imaging of coherent spin wave excitation by surface acoustic waves via magnetoelastic coupling in a layered material system.

Contribution

It introduces a phase-resolved optical method to directly image and analyze coherent spin wave excitation driven by surface acoustic waves.

Findings

Successful direct imaging of resonant spin wave excitation

Clear separation of SAW and SW signals using polarization dependence

Confirmation of coherent coupling between surface acoustic waves and spin waves

Abstract

We use a direct phase-resolved optical technique to study the coherence of spin waves (SWs) that are driven by surface acoustic waves (SAWs) via resonant magnetoelastic coupling. For this, we employ a piezoelectric lithium tantalate (LiTaO$_{3}$) substrate, equipped with micropatterned interdigital transducers for SAW excitation, which interact with SWs in a 5 nm thin and 20 $\mu$m wide Co$_{40}$Fe$_{40}$B$_{20}$-waveguide. We detect the SAW and the SW using a phase-locked micro-focused optical polarization detection experiment and use the characteristic polarization dependence to separate the SAW and SW signals. Our measurements directly image the resonant and coherent excitation of the SW by the SAW.