Modeling flux pinning in thin undoped and BaZrO₃-doped YBCO films

A simple model based on distributions of twin boundaries, dislocations, and BaZrO₃ nanorods is presented to describe the J_c properties of undoped and BaZrO₃ (BZO)-doped YBa₂Cu₃O_x thin films. The model accurately describes the shape of J_c(B,T) curves of the films, when the pinning site distributions are taken from distributions of twin spacings and BZO nanorods from transmission electron microscope images. Thus, assuming that the model can be used for prediction of the J_c properties, we conclude that for enhancement of undoped films more crystalline defects are needed and for doped films a dopant that would create slightly larger rods would be optimal.