Variation of pinning force density throughout the TSMG Y123 superconductor with location

Abstract

Top seeded melt growth (TSMG) Y123 sample with 35 mm diameter was produced by using Nd123 seed and its superconducting parameters such as transition temperature (Tc), critical current density (Jc) and pinning mechanism were locally examined by taking small specimens which are containing defects in different number, size and distribution from different locations throughout the sample. The Tc of the main sample was determined from the resistivity measurement as 93.4 K. It was observed that the Jc was higher in the region close to the seed, while the Jc decreased towards to the edge or the deeper regions of the sample. Effective pinning mechanisms at different temperatures were determined by plotting the curves of the pinning force density (fp) of the specimens versus reduced magnetic field (h= Ha/Hmax) and the locational variations of the fp were examined. It was seen that below the value of h ≈ 0.2, normal point pinning was dominant at 30 and 50 K, while surface pinning was dominant at 77 K, in the all specimens. In addition, a transition was observed between two different pinning mechanisms when the Hmax > h > 0.2. The transition was took place between  and normal point pinning at 30 and 50 K while it was seen between  and surface pinning at 77 K.