Skyrmion Creep and Avalanches

We numerically examine skyrmion motion in systems with random disorder. We find that with increasing temperature, the depinning threshold decreases and a distinct creep regime emerges in which the skyrmion motion occurs in avalanches or jumps. Within the creep regime the skyrmion Hall angle is zero, while at higher drives when the skyrmions start to move continuously, the skyrmion Hall angle becomes finite and increases with increasing drive until it saturates at the intrinsic value. We show that the skyrmion avalanches exhibit a power law size distribution indicative of critical behavior near a depinning point. For systems with moderate to low intrinsic skyrmion Hall angles, the time-averaged avalanche signatures have a symmetric shape, while for high intrinsic skyrmion Hall angles, the avalanche signatures become strongly asymmetric due to the non-dissipative nature of the Magnus force.