Regensburg 2004 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 8: Postersitzung I: Supraleitung
TT 8.8: Poster
Montag, 8. März 2004, 14:30–19:00, Poster A
Understanding grain boundary critical currents in high-Tc superconductors — •Karsten Guth, V. Born, S. Sievers, H. C. Freyhardt, and Ch. Jooss — Institut für Materialsphysik, Universität Göttingen, Tammannstr. 1, 37077 Göttingen
Even more than 15 years after the discovery of high Tc superconductivity current suppression at grain boundary (GB) interfaces is one of the major problems for high current applications.
Therefore, a detailed understanding of current transport across GBs is of great physical and technical interest. We performed a comparative study with thin films of the RE-123 (RE=Y, Y0.8Ca0.2, Yb, Er) system containing small angle GBs. By the manipulation of transport properties via Ca doping, rare earth ion size and the underlying substrate, we were able to directly influence GB properties such as the intergranular critical current.
We used magneto-optical imaging (MOI) to map the magnetic field- and current distribution across thin film GBs. With this space resolved characterisation technique it is further possible to study effects of the magnetic history on the inhomogeneous current distribution of wide current bridges. Additionally, via time resolved MOI the electric field distribution for magnetisation experiments could be calculated from the time-decay of the magentic field distribution, showing electric fields as small as 10−8 V/m in these samples. Our measurements present different routes how to tailor GB properties in the future.