STUDY OF IRREVERSIBILITY LINE OF Y1-XPRXBA2CU3O7-DELTA SINGLE-CRYSTAL

Y1-xPrxBa2Cu3O7-delta (x = 0.1, 0.2, 0.3 and 0.4) single crystals are grown by the flux method. The irreversibility lines of these single cr ystals for external magnetic field parallel to the c axis are measured by SQUID magnetometer. These lines obey the power law given by H = H- 0(1 - T-irr/T-c)(n) with n = 1.5 for low concentrations of Pr (x less than or equal to 0.2), but with n = 2.2 for high concentrations of Pr (x greater than or equal to 0.3). The behavior of the irreversibility lines is discussed in the framework of flux-creep model.