ENHANCEMENT OF FLUX-PINNING BY PR DOPING IN Y1-XPRXBA2CU3O7-DELTA(0-LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-0.4)

Magnetic relaxation measurements in a magnetic field of 5 kOe at temperatures 5 K less-than-or-equal-to T less-than-or-equal-to 90 K have been made on the system Y1-xPrxBa2Cu3O7-delta for 0 less-than-or-equal-to X less-than-or-equal-to 0.4. The measurements reveal two peaks in the normalized logarithmic decay of the magnetization S as a function of temperature for the full range of Pr concentrations studied. The occurrence of the second peak in S could be a reflection of the softening of the flux lattice on approaching the melting line. Both the pinning energy at 27 K and the intragranular critical current density at 10 K exhibit maxima at x = almost-equal-to 0.1-0.2, with values that are about twice the corresponding values at x = 0.