Intrinsic magnetization relaxation properties of Y1:2:3

The intrinsic magnetization relaxation rate R(T) ≡dM(t,T)/dlnt and the pinning potential U0(T) have been determined for single crystalline and melt-textured YBa2Cu3O7 (Y1:2:3) high temperature superconductors of different sizes in their critical state. In contrast to previous reports, R(T) is a monotonically decreasing function and U0(T), deduced from R(T), a monotonically increasing function of temperature. The unusual temperature dependence of U0 is qualitatively explained in terms of a collective flux pinning. The U0-distribution model previously proposed for HTS's is not consistent with certain experimental observations