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TT: Tiefe Temperaturen

TT 24: Vortexdynamik und Pinning

TT 24.5: Hauptvortrag

Freitag, 26. März 1999, 11:00–11:30, F2

Scanning Force Microscopy at Low Temperatures. Vortices in High Transition Temperature Superconductors. — •H.J. Hug¹, P.J.A. van Schendel¹, B. Stiefel¹, O. Knauff¹, R. Hoffmann¹, S. Martin¹, H.-J. G"untherodt¹, B. Dam², and R. Griessen² — ¹Institut für Physik, Universität Basel, Klingelbergstr. 82, CH-4056 Basel — ²Faculteit Natuurkunde en Sterrenkunde Vrije Universiteit De Boelelaan 1081 HV Amsterdam The Netherlands

After a short introduction into the instrumentation, the principles of quantitative magnetic force microscopy will be discussed. The low temperature magnetic force microscope allows to measure both, the topography and the magnetic stray field of a superconducting sample at exatly the same location with high spatial resolution. In laser ablated YBa₂Cu₃O_7−x thin film samples, the rather irregular vortex patterns indicate strong pinning. It will be shown that the pinning centers are mostly line defects due to edge dislocations. In YBCO single crystals the vortex patterns seem to show some ordering, but no 2D long-range order is present. Instead, 1D chains of of regularly spaced vortices running along the <110> directions are observed. Careful analysis of data acquired in fields ranging from 0.5 mT to 0.5 T shows that the twin boundaries dominate possible intrinsic mechanisms for vortex ordering at least in low fields.

In an outlook the possibility of exchange force microscopy and atom manipulation by the low temperature scanning force microscope will be discussed.