Strongly coupled spin waves and surface acoustic waves at room temperature

Hwang, Y.*; Puebla, J.*; 近藤 浩太*; Gonzalez-Ballestero, C.*; 一色 弘成*; Snchez Muoz, C.*; Liao, L.*; Chen, F.*; Luo, W.*; 前川 禎通*; et al.

Physical Review Letters, 132(5), p.056704_1 - 056704_7, 2024/01

https://doi.org/10.1103/PhysRevLett.132.056704

Here, we report the observation of strong coupling between magnons and surface acoustic wave (SAW) phonons in a thin CoFeB film constructed in an on-chip SAW resonator by analyzing SAW phonon dispersion anticrossings. We employ a nanostructured SAW resonator design that, in contrast to conventional SAW resonators, allows us to enhance shear-horizontal strain. Crucially, this type of strain couples strongly to magnons. Our device design provides the tunability of the film thickness with a fixed phonon wavelength, which is a departure from the conventional approach in strong magnon-phonon coupling research. We detect a monotonic increase in the coupling strength by expanding the film thickness, which agrees with our theoretical model. Our work offers a significant way to advance fundamental research and the development of devices based on magnon-phonon hybrid quasiparticles.