Flux Pinning in YBCO Single Crystal Grown on Y2O3 Layer

Abstract

In this study, single-crystal Y123 samples were grown by a cold top-seeding method by using Nd123 seed, and the effect of Y2O3 buffer layer was investigated. The upper critical magnetic field and coherence length were established as 110 T and 17.3 ´ Å, respectively. The dependence of the effective activation energy U of the flux pinning on the magnetic field and temperature of the sample were determined using the Arrhenius activation energy law from the resistivity curves. It was found that the deduced value of the activation energy for a Y123 sample is in good agreement with the corresponding values in YBCO samples. The maximum activation energy value was approximately 0.9 eV in the zero magnetic field. In order to examine the homogeneity of the pinning properties of different layers, rectangular specimens were cut from the sample. AC susceptibility measurement was performed, and it was found that the shifting of the peak temperature (Tp) with an AC magnetic field is small, indicating good pinning properties. The normalized pinning force density versus the reduced field was examined at different temperatures to determine the pinning mechanism. It was found that normal core-type pinning was effective, and in low fields, pinning was only due to Y211 particles.