Flux-line dynamics in YBCO and BSCOO single crystals: thermal activation theory interpretation of magnetization measurements

The flux-line dynamics in YBCO and BSCCO single crystals have been studied over a wide range of frequencies (10 -3 -10 4 Hz) by means of three experimental techniques: AC susceptibility, magnetization decay and magnetization hysteresis loops. The authors propose an approximate scheme that facilitates understanding of observed phenomenology in high-temperature superconductors (HTSC). It is based on the relationship between rho and J as deduced from thermal activation theory. In fact, the rho (J) relationship, reveals that an experiment on HTSC materials can involve an extended range of J values between 0 and J c0 and, thus, an effective pinning potential between U 0 and 0, unlike the situation with low-temperature superconductors (LTSC).