ABSTRACT
Retaining a dissipation-free state while carrying large electrical currents is a challenge that needs to be solved to enable commercial applications of high-temperature superconductivity. Here, we show that the controlled combination of two effective pinning centres (randomly distributed nanoparticles and self-assembled columnar defects) is possible and effective. By simply changing the temperature or growth rate during pulsed-laser deposition of BaZrO(3)-doped YBa(2)Cu(3)O(7) films, we can vary the ratio of these defects, tuning the field and angular critical-current (Ic) performance to maximize Ic. We show that the defects' microstructure is governed by the growth kinetics and that the best results are obtained with a mixture of splayed columnar defects and random nanoparticles. The very high Ic arises from a complex vortex pinning landscape where columnar defects provide large pinning energy, while splay and nanoparticles inhibit flux creep. This knowledge is used to produce thick films with remarkable Ic(H) and nearly isotropic angle dependence.
