Technological applications of NbN thin films may be threatened by the development of magnetic flux avalanches of thermomagnetic origin appearing in a large portion of the superconducting phase. In this work, we describe an approach to substantially suppress the magnetic flux avalanche regime, without compromising the upper critical field. This procedure consists of depositing a thin Nb layer before the reactive deposition of NbN, thus forming a bi-layered system. We use ac susceptibility and dc magnetometry to characterize both the single-layer films, Nb and NbN, and the bi-layered specimen, as well as calibrated magneto-optical imaging to map the instability regime of the studied samples. Magnetic flux imaging reveals interesting features of the dendritic flux avalanches in the bi-layer system, including halo-like patterns and crossing avalanches.

中文翻译：

---

Nb/NbN 薄膜中的磁通量雪崩

NbN 薄膜的技术应用可能会受到出现在大部分超导相中的热磁源磁通量雪崩的威胁。在这项工作中，我们描述了一种在不影响上临界场的情况下显着抑制磁通量雪崩状态的方法。该过程包括在反应性沉积 NbN 之前沉积薄 Nb 层，从而形成双层系统。我们使用交流磁化率和直流磁力计来表征单层薄膜 Nb 和 NbN 以及双层样品，以及校准的磁光成像来绘制所研究样品的不稳定性状态。磁通量成像揭示了双层系统中树枝状通量雪崩的有趣特征，包括晕状图案和交叉雪崩。