Functionalized High-Speed Magnon Polaritons Resulting from Magnonic Antenna Effect

Abstract

Magnon polaritons (MPs) refer to a light-magnon coupled state, which have the potential to act as information carriers, possibly enabling charge-free computation. However, light-magnon coupling is inherently weak. To achieve sufficiently strong coupling, a large ferromagnet or coupling with a microwave cavity is necessary. Thus, we theoretically propose a 100 nm YIG/1 \textmu{}m GGG/500 \textmu{}m YIG structure as a fundamental platform for magnonic and magnon-optical information storage devices to address the aforementioned issues. Furthermore, we discuss the transport properties of the MPs. Owing to the waveguide modes formed by the dielectric constant of the structure, the magnons placed in a nanometer-thin layer are strongly coupled with light. In addition, a longitudinal magnon-magnon coupling between thin and thick magnetic layers yields rich functionalities and a large magnon density to the thick-layer MPs due to the ``magnonic antenna effect.'' Hence, a large, direction-switchable magnon current in the thin layer is observed. The proposed structure indicates a longer coherence length and suitable figure of merit for the magnonic antenna effect. Therefore, the findings of this study would enable the integration of ferromagnetic micro- and nanostructures for MP-based information devices without any restrictions due to cavities.