Vortex avalanches in superconducting/ferromagnetic hybrids*

We study the potential for manipulating ultrafast vortex dynamics in thermo-magnetic avalanches (TMA) using magnetic stripes patterned on top of superconducting films. Tuning the stripe magnetization induces lines of strong magnetic potential for Abrikosov vortices and promotes guided slow vortex motion and directional TMA jumps. The cross-polarized stripes cause the emission of flux branches away from the TMA stamp reducing the TMA power and limiting possible harmful effect of the TMA. We find that TMAs are repeatedly launched from specific spots at the sample perimeter with enhanced barrier for vortex entry. The flux accumulation in these spots followed by accelerated discharge of vortices significantly reduces the threshold of the applied field ramping speed for the TMA creation, which is orders of magnitude smaller than predicted by the existing TMA theory. We observe a regular preferred propagation of the TMA dendrites into maximum trapped flux regions and enhanced TMA activity at the receding branches of magnetization, pointing to the effect of the vortex-antivortex annihilation on the TMA front motion.