Influence of the Gd concentration on superconducting properties in second-generation high-temperature superconducting wires

Systematic studies of second-generation high-temperature superconducting wires with Gd excess relative to the stoichiometric GdBa$_2$Cu$_3$O$_7$ composition are reported. It has been revealed that filamentary defects in the form of non-superconducting Gd$_2$CuO$_4$ phase located along the ab plane are formed during film growth. These inclusions lead to a change in the pinning mechanism of the vortex structure, due to which the peak of the critical current at +15% Gd is clearly observed.