CORRELATIVE MOTION OF VORTICES NEAR THE VORTEX LATTICE MELTING-POINT IN BI2SR2CACU2O8-CRYSTALS(X SINGLE)

Voltage noise of the Bi2Sr2CaCu2O8+x single crystal below T-c is analy sed by an asymptotic power spectrum method. The low-frequency noise po wer, S-v(T), shows a peak at T = T-p. This peak is found to be closely related to the vortex lattice melting temperature. Near the peak T = T-p the power spectrum, S-v(f), exhibits a power-law fall-off, while a t much lower temperatures S-v(f) dramatically deviates from the power- law behaviour, showing some broad peaks which are superposed upon a ba ckground with an exponential-law characteristic. The estimated correla tion dimension of the noise data reveals that the vortex motion is hig hly correlated at the early stage of melting, then develops into an ex tended dissipative dynamic system with self-organized criticality, sho wing a 1/f(alpha) behaviour. The correlated motion disappears when the lattice completely melts.