Dresden 2009 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 28: Superconductivity: Heterostructures, Andreev Scattering, Proximity Effect, Coexistence
TT 28.8: Talk
Wednesday, March 25, 2009, 17:30–17:45, HSZ 105
Magnetic properties and local critical currents of cobalt covered MgB2 films — •Sebastian Treiber1 and Joachim Albrecht2 — 1Max Planck Institut für Metallforschung, D-70569 Stuttgart, Germany — 2HTW Aalen, Beethovenstr. 1, D-73430 Aalen, Germany
At Temperatures below 10K the critical state in MgB2 thin films gets unstable, the magnetic flux percolates filamentary into the superconductor. This state evolves due to chaotic motion of magnetic vortices and leads to dendritic flux density patterns. Since the critical current vanishes inside the dendrites this effect leads to a strong suppression of possible transport currents. We have found, that ferromagnetic cobalt cover layers can influence the flux pinning scenario in the superconductor. Therefore a heterostructure of MgB2 and cobalt was investigated using SQUID magnetometry and magneto-optical (MO) imaging. Two different effects are observed. On the one hand the temperature for the occurrence of flux avalanches is shifted to lower temperatures as observed by MO studies. On the other hand magnetic hysteresis loops obtained by SQUID measurements show a significant asymmetry with respect to the Hext = 0 axis attributed to magnetic effects on flux line pinning [1].
[1] S. Treiber, B. Stuhlhofer, H. - U. Habermeier and J. Albrecht, SUST (submitted)