Side-selective and non-destructive determination of the critical current density of double-sided superconducting thin films

A method is proposed for the side-selective and non-destructive determination of the critical current density (j(c)) of high-T-c, superconducting (HTSC) thin films deposited on both sides of a thin wafer. The method makes use of the alteration of induced voltage in a coil by the superconducting transition in the HTSC thin film. This voltage alteration is measured in dependence on AC current in the coil. In order to obtain the value of the critical current density, the geometry of the induced current density distribution in the HTSC thin film, and from it the induced voltage in the coil, were calculated for T < T-c (full superconducting state of the film) as a function of the distance of film to coil. The finite element approach is used for the calculations. This procedure is applied to the semiautomatic routine characterization of j(c) of double-sided 3-inch diameter HTSC thin films, which are used for optimization of passive microwave devices.