Vortex creep in TFA–YBCO nanocomposite films.

Vortex creep in YBa₂Cu₃O_{7 − x} (YBCO) films grown from the trifluoracetate (TFA) chemical route with BaZrO₃ and Ba₂YTaO₆ second-phase nanoparticles (NPs) has been investigated by magnetic relaxation measurements. We observe that in YBCO nanocomposites the phenomenological crossover line from the elastic to the plastic creep regime is shifted to higher magnetic fields and temperatures. The origin of this shift lies on the new isotropic-strong vortex pinning contribution appearing in these nanocomposites, induced by local lattice distortions. As a consequence, we demonstrate that the addition of non-coherent NPs produces a decrease in the creep rate S in most of the phase diagram, particularly, in the range of fields and temperatures (, ) relevant for large scale applications. [ABSTRACT FROM AUTHOR]