Flux pinning activation energy from levitation force relaxation in a single-grain YBCO bulk superconductor

Abstract

The present study investigates the temperature dependence of the magnetic levitation force for a single-grain YBCO bulk sample with a final diameter of approximately 16 mm and a thickness of approximately 9 mm. This sample was fabricated by the top-seeded melt growth (TSMG) method using an Nd123 seed crystal. The superconducting properties of the single-grain YBCO bulk were examined at various low temperatures (37, 47, 57, 67, and 77 K) using a vibrating sample magnetometer (VSM) and a home-made magnetic levitation force measurement system. The activation energy was estimated from the logarithmic relaxation of the levitation force over the low-temperature range of 37–77 K. The temperature dependence of the estimated activation energy was systematically investigated for a CeO₂-added, TSMG-grown single-grain YBCO bulk superconductor. At 37, 47, 57, 67, and 77 K, the activation energies were found to be 0.078, 0.099, 0.121, 0.143, and 0.166 eV, respectively. The zero-field critical current densities (Jc) were determined to be 19.7 × 104, 12.9 × 104, 8.5 × 104, 5.42 × 104, and 1.96 × 104 A/cm2 at temperatures of 37, 47, 57, 67, and 77 K, respectively. The aim of this study is to improve the understanding of the efficacy of large-scale superconductor levitation across different temperatures.