Critical current of Y1Ba2Cu3O7 in strong applied fields

Abstract

Critical currents of the new high‐temperature superconductor Y₁Ba₂Cu₃O₇ have been measured in applied fields of up to 7 T and for temperatures down to 70 K. We find that the critical current is drastically reduced by the application of magnetic fields much smaller than the upper critical field of the samples, H_c2. This anomalous behavior might be due to very weak pinning, or to a very strong anisotropy of H_c2. H_c2 is found to follow a linear temperature dependence that however extrapolates to a critical temperature higher than that measured directly. This might result from the existence of a percolative structure, or from the presence of a small volume fraction of high critical temperature, high critical field regions.