Europhys. Lett, 47 (1), pp. 110-115 (1999)
Doping-induced enhancement of the critical currents of grain boundaries in
A. Schmehl, B. Goetz, R. R. Schulz, C. W. Schneider, H. Bielefeldt
H. Hilgenkamp and J. Mannhart
Center for Electronic Correlations and Magnetism
Institute of Physics, Augsburg University - 86135 Augsburg, Germany
(received 23 December 1998; accepted 19 April 1999)
PACS. 74.72 - High- compounds.
PACS. 74.60Jg - Critical currents.
PACS. 74.62Dh - Effects of crystal defects, doping and substitution.
The critical current density of grain boundaries in films is increased beyond the hitherto established limit by overdoping the superconductor. Using Ca-doping, values for the critical current density are obtained, that exceed the highest values reported ever for the undoped material by more than a factor of seven. Further, it is found that the overdoping strongly reduces the grain boundary normal-state resistivity. This systematic improvement of the grain boundary transport properties by doping is of great importance for applications of the high- cuprates and gives insight into the mechanisms controlling the grain boundary behavior.
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