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

Abstract

We report ferromagnetic resonance in the normal configuration of an electrically insulating magnetic bi-layer consisting of two yttrium iron garnet (YIG) films epitaxially grown on both sides of a 0.5 mm thick non-magnetic 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 the magneto-elastic interaction. This coherent mediation of angular momentum by circularly polarized phonons through a non-magnetic material over macroscopic distances can be useful for future information technologies. arXiv:1905.12523v3 [cond-mat.mes-hall]

Unidirectional Pumping of Phonons by Magnetization Dynamics

“…The excited phonons below propagate to and are absorbed by the second nanowire. Its dynamics reemits phonons that subsequently interfere with the original ones [20]. Denoting the magnon operators in the left and right nanowires asβ L andβ R [41],…”

“…The phonon pumping [17], i.e., the excitation of bulk sound waves in a high-quality acoustic insulator by the dynamics of a proximity magnetic layer via the magnetoelastic coupling [18,19], may be useful here. Bulk phonons in the insulator gadolinium gallium garnet (GGG) can couple two yttrium iron garnet (YIG) magnetic layers over millimeters [20,21].…”

“…For an analytical treatment, d is assumed to be much smaller than the skin depth of the SAWs, such that the displacement field in the wire is nearly uniform in the z dependence. The lattice and elastic parameters at the YIGjGGG interface match well [17,20,21,36] and are assumed equal. A uniform and sufficiently large static magnetic field H 0 along ⃗…”

Angular momentum conservation and phonon spin in magnetic insulators

“…The quantum dynamics of magnetic rigid rotors has been investigated recently in the context of levitated nanoparticles [22][23][24][25]. Very recently ferromagnetic resonance experiments have shown coherent magnon-phonon coupling over millimeter distances [26].…”

Long-Range Phonon Spin Transport in Ferromagnet–Nonmagnetic Insulator Heterostructures

“…Equipped with the full, analytical solution of the coupled magnetoelastic dynamics (5) and (6), we proceed to calculate various observables characterizing the spin transport through the heterostructure. Throughout the remainder of this Letter, we use parameters of YIG for the magnets and GGG for the nonmagnet [10,12,15], i.e., s = 7.5/nm 3 , ρ = 5170 kg/m 3 , c ⊥ = 3843 m/s, B ⊥ = 6.96 × 10 5 J/m 3 , and α G = 9 × 10 −5 , as well asρ = 7080 kg/m 3 andc ⊥ = 3530 m/s. The metallic leads are taken to be platinum, so that g ↑↓ = 5 nm −2 [16].…”