Flux jumps driven by a pulsed magnetic field

The understanding of flux jumps in the high temperature superconductors is of importance since the occurrence of these jumps may limit the perspective s of the practical use of these materials. In this work, we present the exp erimental study of the role of heavy ion irradiation in stabilizing the HTS C against flux jumps by comparing un-irradiated and 7.5 x 10(10) Kr ion/cm( 2) irradiated (YxTm1-x)Ba2Cu3O7 single crystals. Using pulsed field magneti zation measurements, we have applied a broad range of field sweep rates fro m 0.1 to 1800 T/s to investigate the behavior of the flux jumps. The observ ed flux jumps, which may be attributed to thermal instabilities, are incomp lete and have different amplitudes. The flux jumps strongly depend on the m agnetic field, on the magneto-thermal history of the sample, on the magneti c field sweep rate, on the critical current density j(c), on the temperatur e and on the thermal contact with the bath in which the sample is immersed. (C) 2000 Elsevier Science B.V. All rights reserved.