Abnormal anticrossing effect in photon-magnon coupling

We report the experimental demonstration of an abnormal, opposite anticrossing effect in a photon-magnon-coupled system that consists of an yttrium iron garnet film and an inverted pattern of split-ring resonator structure (denoted as ISRR) in a planar geometry. It is found that the normal shape of anticrossing dispersion typically observed in photon-magnon coupling is changed to its opposite anticrossing shape just by changing the position/orientation of the ISRR's split gap with respect to the microstrip line axis along which ac microwave currents are applied. Characteristic features of the opposite anticrossing dispersion and its linewidth evolution are analyzed with the help of analytical derivations based on electromagnetic interactions. The observed opposite anticrossing dispersion is ascribed to the compensation of both intrinsic damping and coupling-induced damping in the magnon modes. This compensation is achievable by controlling the relative strength and phase of oscillating magnetic fields generated from the ISRR's split gap and the microstrip feeding line. The position/orientation of an ISRR's split gap provides a robust means of controlling the dispersion shape of anticrossing and its damping in a photon-magnon coupling, thereby offering more opportunity for advanced designs of microwave devices.