Unlocking Photon–Magnon Interplay via Saturation Magnetization

Abstract Photon–magnon hybrid systems present a promising platform for the development of next generation devices in quantum information processing and quantum sensing technologies. In this study, we investigate the control of photon–magnon coupling (PMC) strength through systematic variation of the saturation magnetization M s in a planar hexagonal-ring resonator (HRR) integrated with a yttrium iron garnet (YIG) thin film configuration. Using full-wave numerical simulations in CST Microwave Studio, we demonstrate that tuning the M s of the YIG film from 1750 Oe to 900 Oe enables systematic control over the coupling strength across the 127–51 MHz range at room temperature. To explain the observed PMC dynamics, we develop a semiclassical analytical model based on electromagnetic theory, that accurately reproduces the observed coupling behavior, revealing the key role of spin density in mediating the light–matter interaction. The model is further extended to include the effects of variable magnon damping across different M s values, enabling broader frequency control. These findings establish M s as a key tuning parameter for tailoring PMC, with direct implications for the design of tunable hybrid systems for reconfigurable quantum devices.