Crossover between fractal and nonfractal flux penetration in high-temperature superconducting thin films

In this study the role of anisotropy on flux penetration in c-axis epitaxial (Formula presented) and (Formula presented) films is investigated by magneto-optics. We study thin films of (Formula presented) on substrates with vicinal angles of 0° (well-oriented), (Formula presented) and (Formula presented) and (Formula presented) films as a function of chain-conduction-induced anisotropy. A crossover from fractal to nonfractal flux penetration is observed with increasing anisotropy. Numerical simulations of anisotropic flux motion are compared with experiment. © 1998 The American Physical Society.