MAGNETIC-FIELD ANGLE DEPENDENCE OF THE CRITICAL CURRENT DENSITY IN HIGH-QUALITY Bi2Sr2Ca2Cu3Ox THIN FILMS

Critical current densities, J(C), have been investigated in as-deposited Bi2Sr2Ca2Cu3Ox thin films with c-axis orientation, which were prepared by metalorganic chemical vapor deposition (MOCVD). One of these films showed record-high J(C) values for Bi-oxide thin films: 1.3 x 10(10) A/m(2) at 70 K; 10(11) A/m(2) at 30 K. Almost field -independent J(C) was observed in the magnetic fields applied parallel to the film surface (a-b plane) in a wide temperature range (<= 60 K). However, J(C) decreased sharply when the fields were applied in the c-direction, except at low temperatures (<= 20 K). J(C) values measured as a function of the angle between the applied field and the a-b plane, J(C)(H, theta), was determined only by the magnetic field component along the c-direction. That is, J(C)(H, theta) = J(C perpendicular to)(Hsin theta), where J(C perpendicular to)(H) is the critical current density measured in the applied fields perpendicular to the film surface, i.e., in the c-direction. This is clearly explained by the intrinsic pinning theory proposed by Tachiki and Takahashi, which predicts the stepwise flux inclusion into the superconducting specimen.