Dynamic magnetoelastic boundary conditions and the pumping of phonons

Abstract

We derive boundary conditions at the interfaces of magnetoelastic heterostructures under ferromagnetic resonance for arbitrary magnetization directions and interface shapes. We apply our formalism to magnet|nonmagnet bilayers and magnetic grains embedded in a nonmagnetic thin film, revealing a nontrivial magnetization angle dependence of acoustic phonon pumping.

Magnetization dynamics affected by phonon pumping

“…In this limit, and for finite magnetoelastic coupling, phonons just give rise to an average broadening of the FMR line. While indirect, our observations thus confirm the predicted damping enhancement by phonon pumping in the incoherent limit [2,3].…”

“…In the latter, the different phonon modes overlap, leading to a constant contribution of the phonon pumping to the magnon line width. As a consequence, the periodic magnon polaron signatures vanish in favor of a slowly varying additional broadening of the FMR line that was predicted theoretically in the limit of thick GGG substrates [2,3].…”

“…They are coupled by weak magnetoelastic and magnetorotational interactions, which can often simply be disregarded. However, recent experimental and theoretical research reveals that the magnonphonon interaction may cause spectacular effects in (i) ferromagnets close to a structural phases transition such as Galfenol [1,2] or (ii) magnets with exceptionally high magnetic and acoustic quality such as yttrium iron garnet [3][4][5][6][7][8][9].…”

Domain-wall orientation in antiferromagnets controlled by magnetoelastic effects

“…Magnetoelastic effects are usually neglected while considering antiferromagnetic dynamics and switching. However, they can pin the domain walls [1], modify magnon spectra [2][3][4], stabilise antiferromagnetic textures in the finite size samples [5][6][7][8][9][10]. As such, magnetoelastic effects play an important role in the dynamics of antiferromagnets and with the proper tailoring can even open new functionalities.…”

From Elastic Spin to Phonon Spin: Symmetry and Fundamental Relations

“…Since then, the spin angular momentum of the elastic wave is termed as the elastic spin for short, and attracts much attention [13][14][15] as well as the elastic orbital angular momentum counterpart 16,17 . Moreover, the multi-physical interactions between elastic spin of surface acoustic wave and the underlying magnetic materials and piezoelectric materials are attracting more and more attention [18][19][20][21][22][23] . The acoustic spin 10 is the pure longitudinal wave version of elastic spin and phonon spin, firstly observed in experiments 24 , and triggered an upsurge of acoustic spin in complicated structural acoustics [25][26][27] , acoustic spin torque 28,29 and the acoustic spin induced selective directionality and scattering with potential applications [30][31][32] .…”