Strongly Coupled Spin Waves and Surface Acoustic Waves at Room Temperature

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Acoustics

Background:

• Magnon-phonon coupling is crucial for developing advanced spintronic and quantum devices.
• Existing research often faces limitations in tunability and coupling strength.
• Surface acoustic wave (SAW) resonators offer a promising platform for exploring these interactions.

Purpose of the Study:

• To investigate and demonstrate strong coupling between magnons and SAW phonons in a CoFeB thin film.
• To explore the effect of film thickness on magnon-phonon coupling strength.
• To present a novel on-chip SAW resonator design for enhanced magnon-phonon interactions.

Main Methods:

• Fabrication of a nanostructured on-chip SAW resonator with a CoFeB thin film.
• Analysis of SAW phonon dispersion to identify anticrossings, indicative of strong coupling.
• Systematic variation of CoFeB film thickness while maintaining a fixed phonon wavelength.

Main Results:

• Observation of strong coupling between magnons and SAW phonons.
• Demonstration of enhanced shear-horizontal strain in the nanostructured resonator design.
• Monotonic increase in coupling strength with increasing CoFeB film thickness, consistent with theoretical predictions.

Conclusions:

• The study successfully demonstrates strong magnon-SAW phonon coupling in a tunable CoFeB thin-film system.
• The novel resonator design enhances shear-horizontal strain, facilitating stronger interactions.
• This work paves the way for advancements in fundamental research and the development of devices utilizing magnon-phonon hybrid quasiparticles.