Avalanche-driven fractal flux distributions in NbN superconducting films

Flux distributions in thin superconducting NbN films placed in a perpendicular magnetic field have been studied using magneto-optical imaging. Below 5.5 K the flux penetrates in the form of abrupt avalanches resulting in dendritic structures. Magnetization curves in this regime exhibit extremely noi...

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Bibliographic Details
Published in:Applied physics letters 2005-07, Vol.87 (4), p.042502-042502-3
Main Authors: Rudnev, I. A., Shantsev, D. V., Johansen, T. H., Primenko, A. E.
Format: Article
Language:English
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Summary:Flux distributions in thin superconducting NbN films placed in a perpendicular magnetic field have been studied using magneto-optical imaging. Below 5.5 K the flux penetrates in the form of abrupt avalanches resulting in dendritic structures. Magnetization curves in this regime exhibit extremely noisy behavior. Stability is restored both above a threshold temperature T * and applied field H * , where H * is smaller for increasing field than during descent. The dendrite size and morphology are strongly T dependent, and fractal analysis of the first dendrites entering into a virgin film shows that dendrites formed at higher T have larger fractal dimension.
ISSN:0003-6951
1077-3118
DOI:10.1063/1.1992673