Abstract
We have studied the impurity effects on the superconducting transition temperature T c and the upper critical field H c2 in electron irradiated YBa 2 Cu 3 O y with in-plane oxygen defects and YBa 2 (Cu 1-x Zn x ) 3 O y . It is found that the effects of the same type of defects or impurities on T c are the same regardless of the oxygen contents of the samples. Furthermore, T c decreases slower in irradiated YBa 2 Cu 3 O y than in YBa 2 (Cu 1-x Zn x ) 3 O y . This may be well explained by the model that the scattering due to in-plane oxygen defects is more anisotropic than that due to Zn impurities. The different behavior of the reduced slopes (dH c2 /dT) Tc /(dH c2 /dT) Tc0 in these two types of samples can also be understood in this context. ©1999 The American Physical Society.