Magnetic-field anisotropy of high-critical current YBCO coated conductors

High-critical current (>100 A) YBCO thick films, or coated conductors, are being developed for superconductor applications. The critical current I, of these materials exhibits a magnetic-field dependence that depends on the angle of the applied field. Measurement of this anisotropy is critical to the development of high temperature superconductor applications. We have developed the capability to characterize the magnetic-field anisotropy of large, high critical current YBCO superconductors as a function of angle. We have measured the magnetic-field anisotropy of the critical current in the H perpendicular to I orientation of three samples in fields from 0 to 7 T and at temperatures from 75 K to 64 K. The results of these measurements characterize the field dependence of these materials and reveal performance issues of importance to applications. In contrast to previous measurements on thin films, which show that I-c for the H parallel to c orientation has the strongest field dependence, we demonstrate that the intermediate angle of similar to 45 degrees to the normal to the tape plane shows the greatest field dependence for these coated conductors on technical substrates. The field performance, anisotropy, and temperature dependence are discussed in relation to sample quality.