Exchange Magnon-Polaritons in Microwave Cavities

TL;DR

This paper develops a scattering theory to analyze magnon-polaritons in microwave cavities, revealing mode-dependent strong coupling with magnetic films, including spin wave resonances, and demonstrating electrical access via spin pumping.

Contribution

It introduces a comprehensive scattering theory that extends beyond traditional approximations to study mode-dependent strong coupling in magnetic films within microwave cavities.

Findings

Strong coupling occurs for both FMR and SWRs.

Coupling strength decreases with higher mode index.

Electrical control of coupling via spin pumping is possible.

Abstract

We formulate a scattering theory to study magnetic films in microwave cavities beyond the independent-spin and rotating wave approximations of the Tavis-Cummings model. We demonstrate that strong coupling can be realized not only for the ferromagnetic resonance (FMR) mode, but also for spin wave resonances (SWRs); the coupling strengths are mode dependent and decrease with increasing mode index. The strong coupling regime can be also accessed electrically by spin pumping into a metal contact.