Doping-induced enhancement of the critical currents of grain boundaries in $\rm YBa_2Cu_3O_{7-\delta}$

A. Schmehl; B. Goetz; R. R. Schulz; C. W. Schneider; H. Bielefeldt; H. Hilgenkamp; J. Mannhart

doi:doi:10.1209/epl/i1999-00359-2

DOI: 10.1209/epl/i1999-00359-2

Europhys. Lett, 47 (1), pp. 110-115 (1999)

Doping-induced enhancement of the critical currents of grain boundaries in $\rm YBa_2Cu_3O_{7-\delta}$

A. Schmehl, B. Goetz, R. R. Schulz, C. W. Schneider, H. Bielefeldt
H. Hilgenkamp and J. Mannhart

Experimentalphysik VI, 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 ${\rm -h}$ - High- $T_{\rm c}$ compounds.
PACS. 74.60Jg - Critical currents.
PACS. 74.62Dh - Effects of crystal defects, doping and substitution.

Abstract:

The critical current density of grain boundaries in $\rm YBa_2Cu_3O_{7-\delta}$ 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- $T_{\rm c}$ cuprates and gives insight into the mechanisms controlling the grain boundary behavior.

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