Angular dependence of critical current properties in YBCO coated tape under high magnetic field up to 18 T

Critical current properties in a YBCO coated tape have been studied as a function of temperature, magnetic field and field angle under high magnetic field up to 18 T. 1 μm thick YBCO film was deposited on a bi-axially aligned Y₂O₃/YSZ/Hastelloy substrate fabricated by the IBAD technique. The value of critical current, I_c, of the 1 cm wide tape reached as high as 85 A at 77 K in self-field condition. After etching the tape into 100 μm wide and 1 mm long bridge, we measured extended E-J characteristics. The value of critical current density, J_c, is maintained higher than 10⁵ A/cm² at 70 K in 5 T perpendicular to the tape surface. Moreover, the power index n and the so called glass-liquid transition field, B_GL, of the tape in perpendicular field are superior to those of epitaxial film deposited on a SrTiO₃ single crystalline substrate. J_c vs. angle relationship shows broad peak around 90° where field is perpendicular to the tape surface, in addition to a sharp peak at 0°. These results suggest that the tape is highly uniform and correlated defects along c-axis direction contribute to flux pinning.