Volume 35, Number 7, September I 1996
|Page(s)||541 - 546|
|Section||Condensed matter: electronic structure, electrical, magnetic and optical properties|
|Published online||01 September 2002|
Wohlleben effect in small grains of Bi-based high-temperature superconductors: evidence for intrinsic nature of spontaneous currents
II. Physikalisches Institut,
Universität zu Köln,
Zülpicher Str. 77, 50937 Köln, Germany
2 Physikalisches Institut, Universität Karlsruhe - 76128 Karlsruhe, Germany
3 Kazan Institute for Technical Physics, Russian Academy of Sciences, 420029 Kazan, Russian Federation
4 Material Research Center, Department of Physics, University of Groningen Nijenborgh 4, 9747 Ag Groningen, The Netherlands
Accepted: 8 July 1996
We report on the observation of the Wohlleben effect (WE) in powders of Bi-based high-temperature superconductors consisting of isolated grains with sizes of order . In these small grains the Josephson contacts with negative critical current (π-junctions) generally involved to explain the WE must be able to carry a current density of order , even close to Tc. Such high spontaneous currents can be explained, if such contacts are not ordinary tunneling Josephson junctions but superconductor–normal-metal–superconductor junctions and if the superconducting order parameter has d-wave symmetry.
PACS: 74.25.Ha – Magnetic properties / 74.72.Hs – Bi-based compounds / 74.80.Bj – Granular, melt-textured, and amorphous superconductors; powders
© EDP Sciences, 1996
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