Optimization of Spin-Wave Propagation with Enhanced Group Velocities by Exchange-Coupled Ferrimagnet-Ferromagnet Bilayers

Channels for high-speed propagation are interesting for magnonic devices, where spin waves can be used as the information carriers. Unfortunately, exchange-dominated perpendicular standing waves suffer from low group velocities. This study uses a Y${}_{3}$Fe${}_{5}$O${}_{12}$/Ni${}_{81}$Fe${}_{19}$ bilayer in a waveguide structure to enhance the group velocities of spin-wave modes. Other bilayer systems are also explored to optimize the enhancement. This work paves the way to high-performance directional couplers and multifrequency magnonic devices that provide multiple spin-wave modes propagating with high group velocities.