NONLINEAR VORTEX DYNAMICS OF (TL0.5PB0.5)(BA0.2SR0.8)(2)CA2CU3OY SUPERCONDUCTOR IN THE TIME WINDOW OF MILLISECONDS

The complex AC susceptibility of (Tl0.5Pb0.5)(Ba0.2Sr0.8)(2)Ca2Cu3Oy w as measured systematically as a function of temperature T, AC amplitud e, frequency and DC field H-d to study the vortex dynamics in the time window of 10(-4) s-10(-2) s. The dependence of effective barriers of vortex motion on the current density J, H-d and T, U(J, H-d, T), was d etermined. The current relaxation J(t), characteristic curves E(J) and irreversibility lines H-d(T) and critical current densities were stud ied based upon the U(J, H-d, T). It is shown that the AC susceptibilit y technique is a powerful tool in studying vortex dynamics in the time window of milliseconds and estimating the critical current density go verned by flux creep.