Ratchet motion of magnetic skyrmions driven by surface acoustic sawtooth waves

The manipulation of skyrmions by surface acoustic waves (SAW) has garnered significant interest in the field of spintronic devices. Previous studies established that skyrmions can be generated and moved by strain pulses. In this study, we propose that sawtooth-SAWs can be used to drive a ratchet motion of magnetic skyrmions in the presence of pinning centers. This results in a net motion of the skyrmions orthogonal to the continuously applied SAW. The ratchet motion is fundamentally caused by non-vanishing pinning, so that a certain strain gradient magnitude is required to overcome pinning and start skyrmion motion. We demonstrate the feasibility of our concept by micromagnetic simulations and analytical model calculations.表面声波（surface acoustic waves, SAW）对磁斯格明子（skyrmions）的操控在自旋电子学器件领域已引发广泛研究兴趣。既往研究证实，磁斯格明子可通过应变脉冲实现生成与移动。本研究提出，可利用锯齿型表面声波（sawtooth-SAWs）在钉扎中心存在的条件下驱动磁斯格明子产生棘轮运动，使磁斯格明子产生与持续施加的表面声波正交的净运动。该棘轮运动本质源于非零钉扎效应，因此需要达到特定的应变梯度幅值方可克服钉扎，启动磁斯格明子的运动。我们通过微磁模拟与解析模型计算验证了该概念的可行性。