FLUX CREEP IN THE CRITICAL STATE OF A HIGH-TEMPERATURE SUPERCONDUCTOR

We have measured the field and temperature dependences of the logarithmic flux-creep relaxation in an oriented-grain sample of YBaCuO in the critical state. The data indicate that the effective activation energy U0 increases continuously with increasing T between 6 and 30 K, and that U0(T) tends to increase rather than decrease with increasing applied field. These results are compared to predictions of the thermally activated flux-creep model. © 1990 The American Physical Society.