THE IRREVERSIBILITY LINE OF A HIGHLY OXYGENATED MELT-TEXTURED YBA2CU3O7-Y IN T-H-T 3-DIMENSIONAL SPACE

The irreversibility line Tg(H) of a highly textured YBa2Cu3O7 is inves tigated using a fast VSM magnetometer and a SQUID. This line depends s trongly on the time scale of the experiment and the macroscopic size a nd the microstructure of the sample. It is concluded that this line mu st be regarded as a broad crossover region between flux-creep pinning regime and flux-flow regime rather than a clear cut transition between these regimes.