FLUX NOISE IN YBACUO THIN-FILM AND BISRCACUO SINGLE-CRYSTAL

The low frequency noise spectra originating from die temperature induc ed flux relaxation in YBa2Cu3O7-x thin film and Bi2Sr2CaCU2O8 Single c rystal have been recorded using the SQUID magnetometer with the sensit ivity of 100 fWb Hz(-1/2) at 10 Hz. The simultaneous record of the low field AC magnetisation response (susceptibility) shows that the tempe rature at which the maximum of the trapped flux relaxation rate occure s is shifted below the sharp AC response originating from the supercon ducting to the normal state transition. The trapped flux starts to rel ax at considerably lower temperature. The temperature sweep shows that the ''equilibrium'' trapped flux depends only on temperature.