Superstrong coupling of thin film magnetostatic waves with microwave cavity

We experimentally demonstrated the strong coupling between a microwave cavity and standing magnetostatic magnon modes in a yttrium iron garnet film. Such strong coupling can be observed for various spin wave modes under different magnetic field bias configurations, with a coupling strength inversely proportional to the transverse mode number. A comb-like spectrum can be obtained from these high order modes. The collectively enhanced magnon-microwave photon coupling strength is comparable with the magnon free spectral range and therefore leads to the super-strong coupling regime. Our findings pave the road towards designing a new type of strongly hybridized magnon-photon system. (C) 2016 AIP Publishing LLC.