Field sweep rate effect on the flux creep in HTSC

We report the effect of the magnetic field sweep rate on the relaxation of the magnetization as a function of temperature and magnetic field H parallel to the c-axis in an aligned powder, thin film and melt textured YBaCuO superconductors. The real M vs. In t relationship can be deduced from the experimental one by scaling the time t to t+ τ+ t 0. The resulting curves collapse all into a single one. The correlation time τ is calculated and it obeys to the relation (dH/dt) −1 for small T and H. The behavior of the M(In t) curves cannot be described by the Kim-Anderson model for all the explored temperatures and fields.