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 (Nd-Eu-Gd)Ba₂Cu_37-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. The addition of Ag decreases the low-field critical current density, whereas high-field behavior does not change drastically. The results were compared with NdBa₂Cu₃O_7-x single crystals that show various vortex states with increasing defect density. The melt-processed samples demonstrate very similar behavior to the single crystal. The interplay between the point defect and the twin planes resulting an entangled vortex liquid-state remains valid for both single crystals and melt-processed samples