Cavity magnon polariton based precision magnetometry

A photon-magnon hybrid system can be realized by coupling the electron spin resonance of a magnetic material to a microwave cavity mode. The quasiparticles associated with the system dynamics are the cavity magnon polaritons, which arise from the mixing of strongly coupled magnons and photons. We illustrate how these particles can be used to probe the magnetization of a sample with a remarkable sensitivity, devising suitable spin-magnetometers, which ultimately can be used to directly assess oscillating magnetic fields. Specifically, the capability of cavity magnon polaritons of converting magnetic excitations to electromagnetic ones allows for translating to magnetism the quantum-limited sensitivity achieved by state-of-the-art microwave detectors. Here, we employ hybrid systems composed of microwave cavities and ferrimagnetic spheres to experimentally implement two types of novel spin-magnetometers.