Vortex dynamics at high ac amplitudes of trifluoracetate route grown YBa2Cu3O7-x-BaZrO3 nanocomposites

YBa2Cu3O7-x-BaZrO3 (YBCO-BZO) nanocomposites have recently shown to display record pinning forces at high magnetic fields, paving thus the way for power applications. We have applied an ac-susceptibility methodology to analyze the different vortex dynamics of BZO nanocomposites compared to pristine YBCO thin films grown by the trifluoracetate route, close to the irreversibility line. The analysis is focused on the nonlinear Bean critical-state regime, occurring at high ac fields. We determined the dc-field and current-density dependencies of the effective energy barrier for thermally activated flux motion, U-e(J, T, B). The distinctive dependencies encountered for BZO nanocomposites evidence that randomly oriented BZO nanoparticles in the YBCO matrix provide strong-isotropic pinning, even at very high dc fields and temperatures.