High flux pinning in ternary (Nd-Eu-Gd)Ba₂Cu₃O_y superconductors at 77 K

The optimisation of ternary (Nd-Eu-Gd)Ba₂Cu₃O_y (NEG) bulk quasi-crystals has been carried out to achieve high pinning at 77 K. For this purpose we prepared samples with various Nd:Eu:Gd ratios in the NEG compound. Our experimental results suggest that a suitable combination of the three elements on the rare earth site can enhance flux pinning at low, intermediate, and high magnetic fields. This is thus an effective tool for tailoring properties of this material according to requirements of the particular application. We show that the maximum flux pinning can be achieved in the whole magnetic field range (at 77 K) when very fine (sub-micron) secondary phase particles are dispersed in a superconducting 123 matrix with an optimum Nd:Eu:Gd ratio.