Flux pinning in melt-processed ternary (Nd-Eu-Gd) and Nd-based superconductors

We report on the flux pinning and optimization of melt-processed ternary (N d-Eu-Gd)Ba2Cu3O7-x bulk materials using magnetization and magneto-transport (quasi-flux transformer technique) measurements. The highest flux pinning was observed for the optimal annealing condition, where twin planes act as correlated pinning in the presence of the optimal second-phase addition. Th e addition of Ag decreases low-field critical current density, whereas high -field behavior does not change drastically. The results were compared with NdBa2Cu3O7-x single crystals that show various vortex states with increasi ng defect density. The melt-processed samples demonstrate very similar beha vior to the single crystal. The interplay between the point defect and the twin planes resulting an entangled vortex liquid-state remains valid for bo th single crystals and melt-processed samples.