Magnetic skyrmion bubble driven by surface acoustic waves

We study the dynamics of magnetic skyrmion bubble induced by surface acoustic waves (SAWs). We estimate the bubble mass and derive the force due to SAWs acting on a magnetic bubble using Thiele's method. We then study bubble dynamics due to counter-propagating SAWs applied across a nanowire. The strain force is proportional to the strain gradient for dominant strain component and pushes the bubble towards the anti-node of the standing wave where the force vanishes. We find that a magnetic bubble can be pinned to the anti-node of a standing wave and therefore, can be driven by introducing a small detuning between the counter-propagating SAWs. Compared to magnetic domain walls, such pinning is weaker and leads to smaller velocities. In a disk geometry, we propose a SAW-driven skyrmion bubble oscillator with two resonant frequencies. This effect can be potentially applied for the generation of microwaves.