OBSERVATION OF MAGNETOTHERMAL INSTABILITIES IN (YXTM1-X)BA2CU3O7 SINGLE-CRYSTALS IN PULSED MAGNETIC-FIELD MAGNETIZATION MEASUREMENTS

The understanding of flux jumps in the high temperature superconductor s is of importance since the occurrence of these jumps may limit the p erspectives of the practical use of these materials. In this work we p resent the experimental study of the role of heavy ion irradiation in stabilizing the HTSC against flux jumps by comparing un-irradiated and 7.5 . 10(10) Kr-ion/cm(2) irradiated (YxTmi-x)Ba2Cu3O7 single crystal s. Using pulsed field magnetization measurements, we have applied broa d range of field sweep rates from 0.1T/s up to 1800 T/s to investigate the behavior of the flux jumps. The observed flux jumps, which may be attributed to thermal instabilities, are incomplete and have differen t amplitudes. The flux jumps strongly depend on the magnetic field, on the magneto-thermal history of the sample, on the magnetic field swee p rate, on the critical current density j(c), on the temperature and o n the thermal contact with the bath in which the sample is immersed.