Inductive braking of thermomagnetic avalanches in superconducting films
The stabilizing effect of placing a normal metal layer adjacent to a thermomagnetically unstable superconducting film is investigated. By solving the coupled Maxwell and heat transfer equations numerically it is shown that the metal, via inductive braking of the rapidly propagating flux avalanches, strongly reduces their impact. It is found that with increasing thickness and/or electrical conductivity of the metal layer, the number of avalanche events increases, while the amount of flux involved in each avalanche is strongly reduced, resulting in an overall more stable thermomagnetic system. The numerical results provide detailed insight into the braking process, and explain both previous dc magnetometry measurements and new magneto-optical imaging results obtained for a superconducting NbN film coated with a Cu-layer.