High irreversibility fields and current densities in NdBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} single crystals and melt-textured samples
- Forschungszentrum Karlsruhe, Institut fuer Technische Physik, and Universitaet Karlsruhe, Postfach 3640, D-76021 Karlsruhe (Germany)
NdBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} single crystals and melt-textured samples were prepared in reduced atmospheres starting from the Nd-poor side of the phase diagram in order to minimize the Nd/Ba substitution and the second phase content. Current density j and irreversibility field B{sub irr} were measured as a function of temperature and angle between the c axis and applied field direction in samples with different impurity and oxygen contents. Current density vs field shows a pronounced peak effect which results from small clusters of oxygen vacancies, whereas a second peak is related to the twin structure. The current density at 77 K is for fields up to 4 T above 4{times}10{sup 4}A/cm{sup 2} and reaches values of 1.2{times}10{sup 5}A/cm{sup 2} in the peak at 2.1 T. The irreversibility fields parallel to the c axis reach 13.4 and 11.8 T at 77 K in pure and homogeneous single crystals and melt-textured samples, respectively. These extremely high values, which are caused by the twin structure, decrease to 10 and 8 T, respectively, if the current is optimized. The correlation and interference between j and B{sub irr} in the presence of weakly and strongly interacting defects such as small clusters of oxygen vacancies and Nd-422 precipitates, respectively, as well as the influence of the twin structure are analyzed and discussed. {copyright} {ital 1997} {ital The American Physical Society}
- OSTI ID:
- 542255
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 56, Issue 10; Other Information: PBD: Sep 1997
- Country of Publication:
- United States
- Language:
- English
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