| Autor: |
Th. Wolf, I. Apfelstedt, H. Küpfer, A. Turowski, B. Runtsch, R. Meier-Hirmer, C. Keller, U. Wiech, R. Flükiger |
| Rok vydání: |
1989 |
| Předmět: |
|
| Zdroj: |
Cryogenics. 29:268-280 |
| ISSN: |
0011-2275 |
| DOI: |
10.1016/0011-2275(89)90172-0 |
| Popis: |
Intragrain critical current densities of polycrystalline bulk samples and single crystals were investigated by inductive flux profile measurements. In addition to the well known granularity in a polycrystal, granularity within a single crystal was detected. In analogy to the polycrystalline samples increasing values of j c with decreasing size of the powder particles ground from single crystal gives strong evidence for the existence of intragrain junctions. The investigation of the field dependence of j c reveals as a common feature in ceramics and single crystals a maximum at fields far below the upper critical field. This observation and the behaviour of j c in the field region below this maximum are not in accordance with a critical current as expected from a pinning interaction, but rather reveal junction character. This is supported by data of fast neutron irradiation showing a lowering of the junction current, whereas above the critical current maximum j c increases by radiation induced pinning centres. The fields at which the maxima appear are in rough quantitative agreement with the irreversibility line from the glassy state or flux creep model. Once the phase coherence of the intragrain junctions is destroyed by the neutron damage, j c shows the expected continuous decrease with increasing field. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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