Flux pinning property in a single crystal NdBa2Cu3Oy superconductor

The critical current density Jc and the apparent pinning potential U0∗ in a single crystal NdBa2Cu3Oy superconductor which shows a broad peak effect are investigated by measuring a DC magnetization and its relaxation. The field-induced pinning mechanism does not explain the temperature dependence of peak field Bp and dip field Bd. The experimental results of Jc and U0∗ are compared with the theoretical analysis based on the flux creep-flow model, taking the distribution of the flux pinning strength into account. The number of flux lines in the flux bundle (g2), the most probable value of pinning strength (Am) and distribution width (σ2) are determined so that a good fit is obtained between the experimental and theoretical results. The behavior of these parameters is discussed in correspondence to the disorder transition of flux lines.