Nonlinear U(j) dependence determined directly from low-electric-field E-js curves in YBa2Cu3O7- thin films

Journal article (1995)

Authors

H. Wen National Laboratory for Superconductivity, Chinese Academy of Sciences
Z. X. Zhao National Laboratory for Superconductivity, Chinese Academy of Sciences
R. J. Wijngaarden Vrije Universiteit Amsterdam
J. Rector Vrije Universiteit Amsterdam
B. Dam Vrije Universiteit Amsterdam
R. Griessen Vrije Universiteit Amsterdam
Affiliation
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Published Date

1995

Language

English

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Abstract

Low-electric-field E-js curves, normalized dynamical relaxation rate Q(T)=d ln(js)/d ln(E), and experimental critical current density js(E=Ec) were measured from 10 to 85 K with the magnetic sweeping method. By taking a general assumption for the activation energy U(js,T)=Uc(T)f[js(T)/jc(T)], with t=T/Tc, we obtained the U(j,T=0 K) relation by scaling all the E-js curves of different temperatures to one smooth curve with Uc(T) and jc(T) determined by the so-called generalized inversion scheme. It is shown that the important parameter c=ln(v0B), which was actually taken as a fitting parameter in the scaling process in previous work, can be predetermined. It is also found that the resulting U(j,T=0 K) relation based on the E-js curves for T 79 K can be well interpreted with the collective-pinning model. However, the data for T>79 K start to deviate from this interpretation, which may be attributed to the reverse hopping of vortices.