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

Kang An, Zhenhui Hao, Yongzhang Shi, Yingjie Zhu, Xiling Li, Chi Zhang, Guozhi Chai

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.

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

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.
Paper Structure (7 sections, 9 equations, 6 figures, 1 table)

This paper contains 7 sections, 9 equations, 6 figures, 1 table.

Table of Contents

  1. Introduction
  2. Experiments and methods
  3. RESULTS AND DISCUSSION
  4. Experiments of YIG
  5. Experiments of CoFeB
  6. Application Prospects in Integrated Devices
  7. SUMMARY

Figures (6)

  • Figure 1: (a) Sketch of the split-ring resonator structure, showing the placement of the magnetic samples (black rectangle). Microwave signals are input from the input terminal and output from the output terminal.The applied magnetic field is parallel to the microstrip line. (b) Schematic of the interaction between photon and magnon.
  • Figure 2: (a)-(c) In a zero magnetic field, the $S_{21}$ plot for the SRR, the SRR with a YIG film and the SRR with a CFB film.
  • Figure 3: Comparative testing of 100 nm YIG film. (a) Mapping of the amplitude of the transmission coefficient $S_{21}$ as a function of frequency and applied static magnetic field.The coupling region is displayed with magnification in the figure. (b) Mapping of the rate of change of magnetic permeability as a function of frequency and applied static magnetic field. (c) and (d) The coupling of the magnon and photon modes, with the coupling strengths fitted by Eq. \ref{['6']}, is 50 MHz and 54 MHz, respectively.
  • Figure 4: (a)-(c) MPC for the 114.65 nm, 15.92 nm and 5 nm CFB samples. The measured MPC strengths, fitted using Eq. \ref{['6']}, are 350 MHz, 270 MHz and 100 MHz, respectively.
  • Figure 5: (a)-(c) In a zero magnetic field, the $S_{21}$ plot for the SRR, the SRR with GGG and the SRR with Si.
  • ...and 1 more figures