Spin pumping driven by magnon-phonon coupled mode

The properties of magnons and phonons, quasiparticles of spin waves and acoustic waves, have been investigated independently for more than half a century. However, the interaction between magnons and phonons can arise from spin-orbit, dipole-dipole, and exchange interactions in magnetic crystals. The coupling strength is most enhanced in the proximity of the intersection of the uncoupled magnon and phonon dispersions. In the coupling region, the quasiparticle with admixtures of both magnetic and elastic properties, magnon-polarons, is formed.
We report the observation of a resonant enhancement of spin pumping induced by the magnon-phonon coupled mode at room temperature. In this experiment, we measured the spin pumping and inverse spin Hall effect in a Pt/Y₃Fe₅O₁₂ (YIG) bilayer under microwave parametric pumping. We found that spin currents pumped from the YIG layer show an anomaly when the microwave excites dipole-exchange magnons in the proximity of the intersection of the uncoupled magnon and phonon dispersions. Our result shows that the spin pumping driven by the magnon-phonon coupled mode is enhanced compared with the purely magnonic value, consistent with previous works on the spin Seebeck effect.