Berlin 2012 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 33: Superconductivity, Measuring Devices, Matter at Low Temperature: Poster Session

TT 33.23: Poster

Mittwoch, 28. März 2012, 15:00–19:00, Poster B

Unusual flux jumps in MgB₂ thin films — •Sebastian Treiber¹, Claudia Stahl¹, and Joachim Albrecht² — ¹Max-Planck-Institut für Intelligente Systeme, Heisenbergstraße 3, 70569 Stuttgart, Germany — ²Hochschule Aalen, Beethovenstraße 1, 73430 Aalen, Germany

Most superconductors exhibit flux jump phenomena, for example the so called flux avalanches. Below a material dependent threshold temperature - about 10K in case of MgB₂ - flux penetration changes from deterministic to chaotic. In this case, very fast moving vortices form dendritic flux patterns, destroying the critical state along their path. Magneto - optical images show characteristic features of this destruction, like a current - free path of an avalanche. Our experiments have shown, that avalanche behavior can be very different in MgB₂ films with an irregular microstructure [1]. In this contribution, we report on large flux jumps which occur in samples with irregular microstructure at higher temperatures than the classical avalanche temperature. Up to 14K very fast and chaotic flux penetration forms dendritic patterns without destroying the critical state. While SQUID measurements suggest a regular behavior, magneto - optical imaging clearly indicates the presence of large flux jumps.
S. Treiber et al., Phys. Rev. B 84, 094533 (2011)