Flux jumps in YBa2Cu3O7 single crystals at low temperature and fields up to 11 T

Magnetic hysteresis measurements on single crystal YBa2Cu3O7 superconductor s were performed in fields between -11 and 11 T for several temperatures an d held sweep rates with a conventional magnetometer. Many flux jumps have b een observed in the magnetization curves at low temperatures. A decrease of the jump-starting field H-fj with the increase of the field sweep rate and an increase of H-fj with the increase in temperature are observed. It is s hown that the flux jumps depend on the transition temperature of the crysta l. Our results suggest that green phase inclusions improve the magnetic sta bility of the single crystals. (C) 1999 Elsevier Science Ltd. All rights re served.