Selective triggering of magnetic flux avalanches by an edge indentation

We numerically investigate the effect of an edge indentation on the threshold field of thermomagnetic instabilities in superconducting fi lms subjected to a ramping magnetic field, applied perpendicular to the plane of the film. In particuar, we are able to address the question on whether edge indentations promote magnetic flux avalanches. For magnetic field-independent critical current densities model, the triggering of the fi rst magnetic flux avalanche systematically occurs at the edge indentation. In contrast to that, for the more realistic fi eld-dependent critical current density model the fi rst flux avalanche can take place either at or away from the indentation. This selective triggering of magnetic flux avalanches is shown to result from the variation of the threshold magnetic field for the fi rst flux avalanche triggered at the indentation and the reduction of the critical current density by large local magnetic fields at the tip of the indentation which translates in a lower power density dissipated near the tip. We demonstrate that this interplay can be tuned by varying the indentation size, ramp rate of applied fi eld dH/dt, and working temperature T0. We build up a phase diagram in the dH/dt - T0 plane with well-defi ned boundaries separating three distinct regimes of thermomagnetic instability.