Near-isotropic performance of intrinsically anisotropic high-temperature superconducting tapes due to self-assembled nanostructures

We report material and operating parameter conditions where prototype high-temperature superconducting tape conductors exhibit in-plane critical current characteristics that are essentially field orientation independent. This phenomenon is observed for specific magnetic field intensities that depend on the operating temperature and in materials having strong flux pinning by extended nanoscale structures aligned roughly along the crystalline c-axis. The effect can be described by a simple model for the field dependence of critical current density, generalized for anisotropic electronic response. This description may provide insight into means to fine tune the material properties for nearly isotropic performance characteristics at a preferred field and temperature. (c) 2008 American Institute of Physics. [DOI: 10.1063/1.3009286]