Low Temperature Physics: 46, 365 (2020); https://doi.org/10.1063/10.0000868
Fizika Nizkikh Temperatur: Volume 46, Number 4 (April 2020), p. 441-448    ( to contents , go back )

Magnetic flux avalanches in Nb/NbN thin films

L.B.L.G. Pinheiro1,2, M. Caputo3,4, C. Cirillo3,4, C. Attanasio4,3, T.H. Johansen5, W.A. Ortiz2, A.V. Silhanek6, and M. Motta2

1Instituto Federal de São Paulo, Campus São Carlos, 13565-905 São Carlos, SP, Brazil
E-mail: m.motta@df.ufscar.br

2Departamento de Física, Universidade Federal de São Carlos, 13565-905 São Carlos, SP, Brazil

3CNR-SPIN, c/o Università degli Studi di Salerno, I-84084 Fisciano (Sa), Italy

4Dipartimento di Fisica “E.R. Caianiello”, Università degli Studi di Salerno, FI-84084 Fisciano (Sa), Italy

5Department of Physics, University of Oslo, POB 1048, Blindern, 0316 Oslo, Norway

6Experimental Physics of Nanostructured Materials, Q-MAT, CESAM, Université de Liège B-4000 Sart Tilman, Liège, Belgium
pos Анотація:

Received November 25, 2019, published online February 28, 2020

Abstract

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 magnetooptical 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.

Key words: Bi-layer, proximity effect, anti-avalanches, halo-like structure, crossing avalanches.

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