Coherent spin pumping in a strongly coupled magnon-magnon hybrid system

TL;DR

This paper demonstrates coherent spin pumping in a magnon-magnon hybrid system, revealing how interfacial exchange coupling influences damping and linewidth, with experimental validation of theoretical predictions.

Contribution

It provides the first experimental observation of coherent spin pumping in magnon-magnon hybrid modes and links damping effects to interfacial exchange coupling.

Findings

Avoided crossing observed between Py and YIG modes.

Linewidth suppression and enhancement linked to hybrid modes.

Inverse proportionality of torques to Py thickness confirmed.

Abstract

We experimentally identify coherent spin pumping in the magnon-magnon hybrid modes of permalloy/yttrium iron garnet (Py/YIG) bilayers. Using broadband ferromagnetic resonance, an "avoided crossing" is observed between the uniform mode of Py and the spin wave mode of YIG due to the fieldlike interfacial exchange coupling. We also identify additional linewidth suppression and enhancement for the in-phase and out-of-phase hybrid modes, respectively, \textcolor{black}{which can be interpreted as concerted dampinglike torque from spin pumping}. Our analysis predicts inverse proportionality of both fieldlike and dampinglike torques to the square root of the Py thickness, which quantitatively agrees with experiments.