Fast magnetic relaxation close to T_c in YBCO

摘要

We investigated the origin of the normalized decay rate S(T,H) in YBCO compounds. The measurements were carried out on granular RBCO (R, rare-earth elements =Y, Pr, Eu, Gd) ring-shaped samples with randomly oriented grains. The results revealed a correlation between the temperature dependence of the pinning potential and that of the critical current. Such correlation suggests that variations of the Josephson coupling energy, or the order parameter, along the grain boundaries are responsible for the weak flux pinning.