Coherent long-range transfer of angular momentum between magnon Kittel modes by phonons

We report ferromagnetic resonance in the normal configuration of an electrically insulating magnetic bilayer consisting of two yttrium iron garnet (YIG) films epitaxially grown on both sides of a 0.5-mm-thick nonmagnetic gadolinium gallium garnet (GGG) slab. An interference pattern is observed and it is explained as the strong coupling of the magnetization dynamics of the two YIG layers either in phase or out of phase by the standing transverse sound waves, which are excited through a magnetoelastic interaction. This coherent mediation of angular momentum by circularly polarized phonons through a nonmagnetic material over macroscopic distances can be useful for future information technologies

Bright and dark states of two distant macrospins strongly coupled by phonons

8 pages, 5 figuresInternational audienceWe study the collective dynamics of two distant magnets coherently coupled by acoustic phonons that are transmitted through an intercalated crystal. By tuning the ferromagnetic resonances of the two magnets to an acoustic resonance of the crystal, we control a coherent three levels system. We show that the parity of the phonon mode governs the nature of the indirect coupling between the magnets: the resonances with odd / even phonon modes correspond to out-of-phase / in-phase lattice displacements at the magnets, leading to bright / dark states in response to uniform microwave magnetic fields, respectively. The sample is a tri-layer garnet consisting of two thin magnetic layers epitaxially grown on both sides of a half-millimeter thick non-magnetic single crystal. In spite of the relatively weak magneto-elastic interaction, the long lifetimes of the magnon and phonon modes in the sample are the key to unveil this long range strong coupling. This demonstrates that garnets are a great platform to study multi-partite hybridization process between magnon and phonons at microwave frequencies

Couplage à longue portée dans une bi-couche magnétique médiée par les phonons cohérents

We report a ferromagnetic resonance study of an electrically insulating magnetic bi-layer consisting of two yttrium iron garnet (YIG) films epitaxially grown on both sides of a non-magnetic gadolinium gallium garnet (GGG) slab. We show that standing transverse sound waves couple the coherent magnetization dynamics of the two YIG films half millimeter apart through the magnetoelastic interaction, periodically modulating the microwave absorption as a function of frequency. Constructive and destructive interferences between the dynamics of the two YIG layers is observed. This long range coherent coupling by phononic angular momentum currents through non-magnetic dielectric waveguide brings new functionalities to insulator hybrid spin circuits and devices