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Thermomagnetic instabilities in superconducting films: interaction among flux avalanches and non-superconducting regions created intentionally

Grant number: 13/16097-3
Support type:Regular Research Grants
Duration: October 01, 2013 - June 30, 2015
Field of knowledge:Physical Sciences and Mathematics - Physics
Principal Investigator:Fabiano Colauto
Grantee:Fabiano Colauto
Home Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil


Low temperature superconducting films submitted to certain values of magnetic field and temperature are vulnerable to abrupt penetration of magnetic flux. These occurrences arise from a thermomagnetic unbalance, in which instabilities manifest as flux avalanches creating dendritic paths. The speed and size distribution of dendrites are determined by the relative importance of thermal and magnetic diffusion during the process, which can destabilize the superconductor and produce a localized quench. In this circumstance, the superconductor can be partially stabilized by covering it with a normal metallic layer. Thereby, the temporal variation of flux in the metallic layer produce edge current against this variation and brakes the abrupt invasion of flux. In plain films the avalanche development is stochastic, creating different path in each occurrence. In this project we propose to investigate the interaction among flux avalanche and non-superconducting regions created intentionally or regions of normal metal added on certain areas of the superconductors, whose sizes are of the order of the area occupied by an avalanche. A priori, non-superconducting regions may work as reservoir of flux and enhance the system stability. However, the existence of corners in the holes promotes secondary avalanches that spread into the sample. On the other hand, circular holes can arrest avalanches and stabilize the superconductor. Barriers of normal metal added in strategic positions of the sample must brake the flux moving. The magneto-optical imaging technique combined with experiments of magnetization and electric transport will allow a detailed investigation on these superconducting systems. (AU)

Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
CARMO, D.; COLAUTO, F.; DE ANDRADE, A. M. H.; OLIVEIRA, A. A. M.; ORTIZ, W. A.; JOHANSEN, T. H. Trapping Flux Avalanches in Nb Films by Circular Stop-Holes of Different Size. IEEE Transactions on Applied Superconductivity, v. 25, n. 3 JUN 2015. Web of Science Citations: 8.
COLAUTO, F.; MOTTA, M.; PALAU, A.; BLAMIRE, M. G.; JOHANSEN, T. H.; ORTIZ, W. A. First Observation of Flux Avalanches in a-MoSi Superconducting Thin Films. IEEE Transactions on Applied Superconductivity, v. 25, n. 3 JUN 2015. Web of Science Citations: 8.

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