EVIDENCE FOR FLUX-PINNING INDUCED BY SPATIAL FLUCTUATION OF TRANSITION-TEMPERATURES IN SINGLE-DOMAIN (Y1-XPRX)BA2CU3O7-DELTA SAMPLES

The current density j(s) has been measured versus temperature at B = 1 T for single domain (Y1-xPrx)Ba2Cu3O7-delta (x = 0.00, 0.03, 0.05, 0. 08) samples. It is found that the measured current density j, is enhan ced by the substitution of Y with Pr, which manifests that extra pinni ng centers have been introduced into the samples. Detailed analysis sh ow that the temperature dependence of the measured current density j(s )(T) as well as the normalized relaxation rate S(T) for all the four s amples can be well explained basing on the model for flux pinning;indu ced by the spatial fluctuation of the transition temperatures, while t he theoretical results obtained basing on the model for flux pinning i nduced by the spatial fluctuation of the charge carrier mean free path are completely inconsistent with the experiment data. Finally we conc lude that the dominant pinning in our samples are resulted from the sp atial fluctuation of the transition temperatures rather than the mean free path.