Resonant phonon-magnon interactions in free-standing metal-ferromagnet multilayer structures

TL;DR

This paper explores how to design free-standing metal-ferromagnet multilayers to achieve and tune strong resonant interactions between magnons and phonons, enabling detailed study of magneto-elastic coupling at high frequencies.

Contribution

It proposes a novel multilayer design that allows for tuning and observing resonant phonon-magnon interactions across a broad GHz frequency range.

Findings

Resonant interactions can be tuned via multilayer design.

Magnetic field sweeps enable observation of mode coupling.

Frequency range extends up to hundreds of GHz.

Abstract

We analyze resonant magneto-elastic interactions between standing perpendicular spin wave modes (exchange magnons) and longitudinal acoustic phonon modes in free-standing hybrid metal-ferromagnet bilayer and trilayer structures. Whereas the ferromagnetic layer acts as a magnetic cavity, all metal layers control the frequencies and eigenmodes of acoustic vibrations. The here proposed design allows for achieving and tuning the spectral and spatial modes overlap between phonons and magnons that results in their strong resonant interaction. Realistic simulations for gold-nickel multilayers show that sweeping the external magnetic field should allow for observing resonantly enhanced interactions between individual magnon and phonon modes in a broad range of frequencies spanning from tens of GHz up to several hundreds of GHz, which can be finely tuned through the multilayer design. Our results would enable the systematic study and the deep understanding of resonantly enhanced magneto-elastic coupling between individual phonon and magnon modes up to frequencies of great contemporary fundamental and applied interest.