Oxygen content and disorder effects on the critical current density in YBa₂Cu₃O_x

Magnetic measurements have been used to evaluate the critical current density J_c for YBa₂Cu₃O_x samples with various oxygen content (x) and, for partially oxygenated samples (x to approximately 6.5), with different degrees of oxygen disorder. The current density has been expressed in terms (T/T_c)^-δ, where δ decreases linearly with x for x<6.6 and becomes constant for 6.6<x<7. Moreover, the variation in T_c with oxygen content has been used to represent J_c as J_c = J_o (x/T_c)^-n, where J_o is almost constant and n is temperature dependent. At a given temperature ratio (T/T_c), the oxygen disorder enhances the critical current density and weakens its field dependence. It is argued that the increased number of Cu(1)+30 clusters with increasing disorder may cause additional pinning centres and affect the J_c behaviour.