Berlin 2005 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 36: Superconductivity - Vortex Dynamics, Vortex Phases, Pinning

TT 36.1: Vortrag

Mittwoch, 9. März 2005, 10:00–10:15, TU H2053

Vortex Pinning and Magnetization Reversal Observed in Real Space by Magnetic Force Microscopy — •Alexander Schwarz¹, Marcus Liebmann², Ung Hwan Pi³, and Roland Wiesendanger¹ — ¹IAP, University of Hamburg, Jungiusstr. 11, 20355 Hamburg, Germany — ²Department of Mechanical Engineering, Yale University, 15 Prospect Street, New Haven, CT06511, USA — ³ETRI, Gajeong dong Yuseong gu, Daejeon 305-350, South Korea

Vortex pinning mechanisms are important for an understanding of the magnetic properties of high temperature superconductors. Since magnetic force microscopy is able to image individual vortices and the surface topography in the same sample area, it is an ideal tool to study trapping characteristics of defects. In this study, we investigate a Bi₂SrCa₂Cu₂O_8+δ plate-like single crystal with artificial c−axis columnar defects and intrinsic line defects. The later can be identified as either stacking fault dislocations or surface steps. Columnar defects typically trap only one quantum flux. In regions where only columnar defects are present the vortex density follows the transversal Bean model. On the other hand, stacking fault dislocations can accommodate large numbers of vortices and exhibit an anisotropic pinning behavior, i.e., strong transversal, but weak longitudinal pinning [1]. As a result, they impede vortex propagation during magnetization reversal perpendicular to their orientation and strongly alter the flux distribution in their vicinity. Finally, surface steps apparently do not act as pinning centers at all.

[1] U. H. Pi et al., Phys. Rev. B 69, 094518 (2004).