Peak effect in field trapping properties of large grain Dy-Ba-Cu-O/Ag bulk superconductors

The effect of Dy₂BaCuO₅ (Dy211) contents on the field trapping properties of Ag-added Dy-Ba-Cu-O 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 field dependence of their trapped magnetic fields was measured using a Hall probe sensor at 77 K. In the case of the Dy-Ba-Cu-O bulk with excess 5 mol% of Dy211, the peak was found at around 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. On the other hand, the Dy-Ba-Cu-O bulk with excess 40 mol% of Dy211 did not exhibit the peak effect. These results reflect the secondary peak effect in J_c-B properties of the bulk samples.