Local Self-Field Measurements in Tl-2223 Polycrystalline Superconductors

Abstract

We report local self‐field measurements on superconducting (Tl‐2223) disks in an applied field. The axial components of the self‐field generated by polycrystalline superconductors, have been measured at points above the sample using a Hall probe. The measurements were conducted with a computer controlled precision x–y scanning assembly, at liquid nitrogen temperatures. Single point and two‐ dimensional distributions of the local self‐field above the samples immersed in a homogeneous applied field up to 16 mT, were recorded. In an increasing/decreasing magnetic field the magnetic response of the superconductors traverses hysteresis loops due to inter‐ and intragranular flux pinning. The field for full flux penetration and the maximum shielded field have been identified from characteristic points on the hysteresis loops. Evaluation of the average intergrain current density jc, assuming a uniform critical current density, resulted in the value 2.7 × 106 A/m2.