Magneto-optical imaging and electromagnetic study of YBa2Cu3O7 vicinal films of variable thickness

Magneto-optical imaging (MO) and electromagnetic studies have been applied to measure anisotropy and critical currents (Jc) of YBa2Cu3O7 (YBCO) films with variable thickness of 0.2, 0.5, 1.0, 2.0, and 3.0μm deposited on flat and vicinal SrTiO3 substrates of 10degree miscut angle (θs). The flat films nucleated in island-type mode and developed with a dominant c-axis orientation with minority misoriented grains at larger thickness of overall dense structure. The vicinal films, on the other hand, nucleated in step-flow mode and developed with a highly porous structure and minimal density of misoriented grains and impurity phases at large thickness. The difference in the microstructures of these two types of films results in different Jc vs. thickness behaviors. The MO images showed that the magnetic flux penetration in the flat samples is isotropic at all thicknesses, while it is highly anisotropic in the vicinal samples. The anisotropy decreases with film thickness and temperature. These results correlate with distinctive patterns of microstructural evolution in flat and vicinal YBCO films with increasing thickness.