Enhancement of acoustic spin pumping by acoustic distributed Bragg reflector cavity

Surface acoustic waves (SAWs) in the GHz frequency range can inject spin currents dynamically into adjacent nonmagnetic layers via spin pumping effect associated with ferromagnetic resonance. Here, we demonstrate an enhancement of acoustic ferromagnetic resonance and spin current generation by a pair of SAW reflector gratings, which form an acoustic analogue of the distributed Bragg reflector cavity. In the experiment, we confirmed 2.04 $\pm$ 0.02 times larger SAW power absorption in a device with cavity than in case of no acoustic cavity. We confirmed up to 2.96 $\pm$ 0.02 times larger spin current generation by measuring electric voltages generated by the inverse Edelstein effect (IEE) at the interface between Cu and Bi$_2$O$_3$. The results suggest that acoustic cavities would be useful to enhance the conversion efficiency in SAW driven coupled magnon-phonon dynamics.

吉赫兹频率范围的表面声波（SAW）能够通过与铁磁共振相关的自旋泵浦效应将自旋流动态注入相邻的非磁性层。在此，我们展示了一对表面声波反射光栅可增强声铁磁共振以及自旋流的产生，这对光栅形成了分布式布拉格反射器腔的声学类似物。在实验中，我们证实有腔器件中的表面声波功率吸收比无声腔情况大$2.04\pm0.02$倍。通过测量铜和三氧化二铋（Bi₂O₃）界面处逆爱德斯坦效应（IEE）产生的电压，我们证实自旋流产生量增大了$2.96\pm0.02$倍。结果表明，声腔对于提高表面声波驱动的磁振子 - 声子耦合动力学中的转换效率是有用的。