Effect of Dy₂BaCuO₅ addition on trapped magnetic fields in Dy-Ba-Cu-O bulk superconductors

The effect of Dy₂BaCuO₅ (Dy211) contents on the field trapping properties of Ag-added DyBa₂Cu₃O_y (Dy123) single domain bulk has been investigated. The Dy-Ba-Cu-O/Ag bulks 32 mm in diameter with different Dy211 contents were fabricated in air with the top-seeded melt-growth method using NdBa₂Cu₃O₇ seed crystal. The trapped magnetic fields were measured as a function of external field and compared with the J_c-B properties, in that a similar field dependency was observed. In the case of the Dy123 bulk with excess 5 mol% Dy211, the peak was found at around 0.5-1.5 T of external field in the trapped field measurement at 77 K. The value of trapped field was 1.2 T at the peak field. This result reflects the secondary peak effect in J_c-B properties of the bulk samples. On the other hand, the trapped field of Dy123 bulk with excess 40 mol% of Dy211 exhibited 1.4 T when the applied field was removed. This value monotonously decreased with increasing external field, since this sample showed no secondary peak effect in J_c-B properties.