Reentrant stability of superconducting films and the vanishing of dendritic flux instability

Abstract

We propose a mechanism responsible for the abrupt vanishing of the dendritic flux instability found in many superconducting films when an increasing magnetic field is applied. The onset of flux avalanches and the subsequent reentrance of stability in NbN films were investigated using magneto-optical imaging, and the threshold fields were measured as functions of critical current density ${j}_{c}$. The results are explained with excellent quantitative agreement by a thermomagnetic model published recently [D. V. Denisov et al., Phys. Rev. B 73, 014512 (2006)], showing that the reentrant stability is a direct consequence of a monotonously decreasing ${j}_{c}$ versus field.