Regensburg 2010 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 2: SC: Applications and Measuring Devices

TT 2.4: Talk

Monday, March 22, 2010, 11:00–11:15, H19

Barriers for vortex avalanche propagation in MgB₂ thin films — •Sebastian Treiber¹ and Joachim Albrecht² — ¹Max-Planck-Institut für Metallforschung, Stuttgart, Germany — ²Hochschule Aalen, German

At temperatures below 10K the critical state in MgB₂ thin films gets unstable. This leads to chaotic motion of magnetic vortices and dendritic flux density patterns. Since the critical current is zero inside the dendrites this effect leads to a strong suppression of possible transport currents.

We prepared MgB₂ films containing areas of different current densities and thermal conductivities, respectively. Magneto-optical investigations revealed that the propagation of vortex avalanches can be manipulated by this local variations. It is found that boundaries to areas of higher current density or enhanced thermal conductivity can act like a barrier for the dendrites. The investigations also show that the critical current density around the dendrites is not constant which can not be described by classical critical state models.