In-situ Control of the Photon-Magnon Synchronized Mode in a Miniaturized Magnetometer

Photon-magnon synchronized modes (PMSMs) provide a route for magnetic-field sensing by exploiting their enhanced field responsivity due to cusp points (CPs). However, the previous PMSM magnetometer relies on bulky discrete components and lacks in situ control of photon-magnon interactions, limiting its integration and adaptability. Here, we demonstrate a miniaturized PMSM magnetometer integrated on a printed circuit board. A variable resistor is used to tune the photon-magnon coupling strength in situ. By adjusting the variable resistor, the electromagnetic boundary condition of the magnetometer is altered; hence, the reservoir-mediated photon-magnon interaction is changed. The coupling strength shows a non-monotonic dependence on the reflection coefficient adjusted by the variable resistor and reaches its minimum at the impedance matching condition. Furthermore, we develop a non-Hermitian model with standing-wave interference to describe the PMSM dispersion and derive the critical condition for CP formation. This work realizes a compact and tunable PMSM magnetometer and provides a pathway for controlling photon-magnon interactions in integrated magnetic sensing systems.