Relaxation of the transport critical current in deoxygenated YBa2Cu3O7-delta

We present a study of the transport critical current relaxation for a set o f carefully deoxygenated YBa2Cu3O7-delta polycrystalline samples, in such a way that the oxygen losses mostly come from the intergrain region, while t he grains remain essentially unchanged. The dependence of the relaxation ra tes on the maximum magnetic fields applied to the sample, in the remanent s tate, is consistent with the predictions of a phenomenological model, in wh ich the thermally activated relaxation of the intragrain magnetization prov okes a time decay of the intergrain local fields, thus producing a temporal increase of the transport critical current. (C) 2002 Elsevier Science B.V. All rights reserved.