Dresden 2006 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 33: Superconductivity: Vortex Dynamics, Vortex Phases, Pinning

TT 33.4: Vortrag

Freitag, 31. März 2006, 11:00–11:15, HSZ 304

Bending of magnetic avalanches in MgB₂ thin films — •J. Albrecht^1,2, A. T. Matveev^1,2, M. Djupmyr¹, H.-U. Habermeier², and G. Schütz¹ — ¹Max-Planck-Institut für Metallforschung, Heisenbergstr. 3, 70569 Stuttgart — ²Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, 70569 Stuttgart

The penetration of magnetic flux lines into a superconductor above the lower critical field happens not necessarily in a regular way. It is found that under particular conditions a chaotic penetration in form of magnetic avalanches occurs. These avalanches are closely related to the so called thermomagnetic instability, which identifies local heating due to flux line movement as the origin of the effect. In case of MgB₂ thin films these avalanches are found only below T=10 K and are suppressed by a covering metallic layer with high thermal conductivity and sufficient thickness. These avalanches are observed in case of partly gold covered MgB₂ films by the magnetooptical Faraday-effect. The investigation of avalanches propagating into a gold covered region revealed a change of the propagation direction depending on the incident angle of these avalanches.