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Volumn 48, Issue 18, 1993, Pages 13798-13816

Limits to the critical current in high-Tc superconducting tapes

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Indexed keywords


EID: 0001682963     PISSN: 01631829     EISSN: None     Source Type: Journal    
DOI: 10.1103/PhysRevB.48.13798     Document Type: Article
Times cited : (168)

References (77)
  • 6
    • 84927339291 scopus 로고    scopus 로고
    • A.P. Malozemoff, Superconductivity and its Applications, AIP Conf. Proc. No. 251, edited by Y.H. Kao et al. (American Institute of Physics, New York, 1992), p. 6.
  • 10
    • 84927339290 scopus 로고    scopus 로고
    • The condition for the Josephson interlayer coupling is ξz ll s, where ξz is the superconducting correlation length along c axis and s is the interlayer spacing. This condition can be rewritten in the form (Tc-T)/Tc gg ξab2(0)/γ2s2 where ξab(T) is the correlation length in the ab plane and γ is the anisotropy ratio. For Bi Compounds ξab(0) approx 25 AA and s=15 AA for Bi 2:2:1:2 and 18 AA for Bi 2:2:2:3. The anisotropy ratio for Bi 2:2:2:3 is about 30 according to Hc2 measurements near Tc;
  • 12
    • 84927339289 scopus 로고    scopus 로고
    • This value is probably a lower limit for γ. For Bi 2:2:1:2 a lower limit for the anisotropy ratio at high temperatures seems to be about 200;
  • 14
    • 84927339288 scopus 로고    scopus 로고
    • Therefore, the Josephson regime is important practically at all temperatures below Tc in the Bi compounds.
  • 15
    • 84927339287 scopus 로고    scopus 로고
    • It is also possible that impurities present during the fabrication process tend to concentrate preferentially along a and b axis boundaries outside of colony boundaries, further weakening those weak links.
  • 42
    • 84927339281 scopus 로고    scopus 로고
    • The pinning energy of a single pancake vortex by a columnar defect can be estimated as the core energy of a 2D vortex. This energy is approxΦ0sup 2s/16π2λab2, where λab is the penetration depth for the current along the ab plane. For s=18 AA, λab=2000 AA we obtain an energy close to 70 meV.
  • 43
    • 84927339279 scopus 로고    scopus 로고
    • We note that in tapes a and b axis weak links and secondary phase boundaries are equivalent to columnar defects from the point of view of pinning because the superconducting order parameter is strongly reduced inside these boundaries. However, the concentration of such defects is quite small in comparison to the number of intragranular defects. For this reason is probably reasonable to neglect the effect of these defects. In fact, the influence of grain boundaries on the critical current was not found in the case of textured Bi 2:2:1:2 bulk samples as compared with epitaxial films; see Ref. onlineciteschmitt.
  • 48
    • 84927339271 scopus 로고    scopus 로고
    • Note that we calculated the thermodynamical critical current which can be probed by static measurements. In the presense of transport current through the junction at nonzero temperature the voltage should appear at any current due to vortex fluctuations. For finite junction without vortices similar effect was calculated by Ambegaokar and Halperin;
  • 51
    • 84927339270 scopus 로고    scopus 로고
    • W.E. Lawrence and S. Doniach, in Proceedings of the 12th International Conference on Low Temperature Physics, Kyoto 1970, edited by E. Kanda (Keigaku, Tokyo, 1970).
  • 53
    • 84927339269 scopus 로고    scopus 로고
    • The thermal averaging of the current is an exact procedure. In the case of disorder caused by pinning centers, the average current may not be very significant if the current fluctuations are large. The latter are certainly important when the average current becomes very small, as in the case for the Fraunhofer dependence of the critical current on a magnetic field parallel to the junction;
  • 55
    • 0001235373 scopus 로고
    • Here we consider only the case of a sufficiently large critical current so that the effect of fluctuations can be ignored. This approximation is correct because many uncorrelated weak links contribute to the total current.
    • (1970) Sov. Phys. JETP , vol.31 , pp. 800
  • 65
    • 84927339268 scopus 로고    scopus 로고
    • The account of the vortex fluctuations should make this value smaller;


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.