P. Manuel, VORTEX LINES IN LAYERED SUPERCONDUCTORS .2. PINNING AND CRITICAL CURRENTS IN HIGH-TEMPERATURE SUPERCONDUCTORS, Journal de physique. III, 4(2), 1994, pp. 209-233
Citations number
52
Categorie Soggetti
Material Science","Phsycs, Fluid & Plasmas","Physics, Applied
In this article, a qualitative survey is given on the various phenomen
a which influence the critical current of high temperature superconduc
tors. Critical current is defined as a property related to a non-zero
electric field criterion, the level of which is fixed by experimental
considerations, or efficiency requirements of applications. The presen
tation is restricted to extrinsic intragranular critical current, whic
h depends in a complex way on the interplay between the characteristic
s of pinning centres and the properties of the vortex lattice. The dis
cussion is focussed on the configuration B // c, which contains the ma
in elements of this problem. Differences of behaviour between Y(123) a
nd BSCCO (Bi(2212) or Bi(2223)) are analysed in the context of their r
espective anisotropy factors. Possible regimes for pinning and creep a
re discussed in various temperature domains. From critical current res
ults, a strong pinning regime is found to occur in BSCCO, whereas the
pinning strength in Y(123) is still an open question. The thermal decr
ease of critical current allows a collective creep regime to appear in
both materials, but at different temperature ranges. The disappearanc
e of correlation effects near the irreversibility line results in a fa
ll of the effective pinning energy. We show that in BSCCO, the effecti
ve pinning energy deduced from experimental results is not in agreemen
t with pinning by randomly dispersed oxygen vacancies. Finally, we sho
rtly describe the microstructures which could allow a more efficient p
inning in future materials.