Critical currents and pinning mechanisms in directionally solidified YBa{sub 2}Cu{sub 3}O{sub 7}-Y{sub 2}BaCuO{sub 5} composites
- Instituto de Ciencia de Materiales de Barcelona, Consejo Superior de Investigaciones Cientificas, Campus Universitat Autonoma de Barcelona, Bellaterra 08193 (Spain)
- High Magnetic Field Laboratory, 25 Avenue des Martyrs, Boite Postale 166, F 38042 Grenoble Cedex 9 (France)
The superconducting properties of directionally solidified YBa{sub 2}Cu{sub 3}O{sub 7}-Y{sub 2}BaCuO{sub 5} composites, with critical currents above 10{sup 5} A/cm{sup 2} at 77 K and zero magnetic field, are reported in a wide variety of samples having very different contents of Y{sub 2}BaCuO{sub 5} (211 phase) precipitates with different particle size and magnetic fields up to 22 T. The field, temperature, and composition dependence of the critical currents allow us to identify interfacial pinning by 211 precipitates as a very effective pinning mechanism. Nevertheless, single vortex interfacial pinning has a dominant role only in a narrow region below about 1 T and temperatures 40 K{le}{ital T}{le}80 K. In this region the system shows a behavior very akin to that observed in ion irradiated single crystals and described as correlated disorder. On lowering the temperature the thermal wandering of the vortex from secondary weak pinning centers decreases leading to a new single vortex pinning regime extending up to very high magnetic fields where a mixture of strong and weak pinning centers are active. On the other hand, increasing the magnetic field, the characteristic footprints of the small bundle and large bundle regimes are identified at intermediate temperatures. The former is found below the {ital H}-{ital T} line given by the maximum of the macroscopic pinning force while the latter is observed above this line up to the irreversibility line. Finally, collecting all these results together a magnetic phase diagram of the mixed state of the YBa{sub 2}Cu{sub 3}O{sub 7}-Y{sub 2}BaCuO{sub 5} textured composites is proposed. {copyright} {ital 1996 The American Physical Society.}
- OSTI ID:
- 278716
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 53, Issue 5; Other Information: PBD: Feb 1996
- Country of Publication:
- United States
- Language:
- English
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