The intrinsic surface impedance of coated conductors

Coated conductors, i.e. superconducting thin films grown on tapes consisting in metallic substrates, is an enabling technology for the use of the high-T _c YBa₂Cu₃O_7-δ superconductor in applications requiring long superconducting cables, such as high field magnets and electric power distribution grids. The largely used d.c. measurements of the material current carrying capabilities would benefit from being integrated and complemented by local measurements of the material complex a.c. resistivity. Despite the potential of this approach, high frequencies measurements are hindered by the highly conducting substrate, which obscures the superconductor response. In this manuscript we address the problem of extracting the superconductor impedance by properly taking into account the substrate contribution. (paper)