Study of Magnon-Photon Coupling in Ultra-thin Films Using the Derivative-Divide Method

TL;DR

This paper introduces a derivative-divide method to detect and analyze magnon-photon coupling in ultrathin films, enabling clearer observation of coupling phenomena in nanoscale magnetic materials.

Contribution

The study demonstrates the effectiveness of the derivative-divide analysis in isolating magnetic signals and resolving anticrossings in ultrathin films, advancing characterization techniques for miniaturized magnonic devices.

Findings

Able to measure coupling in films as thin as 60 nm and 5 nm

Successfully isolates magnetic contributions from photon-dominated spectra

Establishes a simple, sensitive method for ultrathin film characterization

Abstract

Magnon-photon coupling in cavity magnonic systems offers a promising route toward integrated wave-based information-processing devices. However, in ultrathin magnetic films the weak magnon response is easily buried beneath photon-dominated spectra. We show that a derivative-divide analysis of the microwave transmission parameter in a planar split-ring-resonator cavity isolates the magnetic contribution and resolves clear anticrossings in yttrium iron garnet and CoFeB films, yielding measurable coupling down to thicknesses of 60 nm and 5 nm, respectively. These results establish derivative-divide method as a simple and sensitive probe of magnon-photon coupling in ultrathin insulating and metallic films, and as a practical tool for characterizing miniaturized cavity-magnonic devices.