Acoustic parametric pumping of spin waves

• We study the parametric excitation of spin waves by longitudinal acoustic waves.
• The threshold of instabilities are investigated.
• The DC spin pumped current and the induced detectable DC voltage is perused.

Recent experiments demonstrated generation of spin currents by ultrasound. We can understand this acoustically induced spin pumping in terms of the coupling between magnetization and lattice waves. Here we study the parametric excitation of magnetization by longitudinal acoustic waves and calculate the acoustic threshold power. The induced magnetization dynamics can be detected by the spin pumping into an adjacent normal metal that displays the inverse spin Hall effect.