| Autor: |
G. Saemann-Ischenko, P. Schmitt, H.-W. Neumüller, Günter Ries, R. Busch, M. Leghissa, Peter Kummeth |
| Rok vydání: |
1993 |
| Předmět: |
|
| Zdroj: |
Journal of Alloys and Compounds. 195:379-385 |
| ISSN: |
0925-8388 |
| DOI: |
10.1016/0925-8388(93)90762-c |
| Popis: |
We investigated the voltage-current (V-I) characteristics in polycrystalline, melt textured and epitaxially grown Bi-2212 superconductors, in Bi-2223 melt textured Ag tapes and in Y-123 films. In all samples the V-I curves are well described by a power law behaviour V ∝ I P over many orders of magnitude in the voltage V. With increasing magnetic field and temperature the exponent p decreases with 1/B from a maximum at p=10–20 down to the ohmic limit p=1. In a double logarithmic plot the V-I lines extrapolate to a common hinge point. These results are interpreted within the frame of thermally activated flux creep. From the measurements on thin films and bulk of Bi 2 Sr 2 CaCu 2 O x we derive an expression for an effective activation energy U eff (B,T,j)=60 meV/B (1-T/T c ) 5/2 ln j o /j. We show that a number of experimental observations are in accordance with this explicit result. In particular (a) exponential decay of the critical current density with field, (b) nonlogarithmic flux creep and (c) the irreversibility field B irr (T) emerge as consequences of the specific functional dependence of U eff . |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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