AN EASY AND NONDESTRUCTIVE INDUCTION METHOD TO CHARACTERIZE SUPERCONDUCTING MATERIALS WITH PLANAR GEOMETRY

A simple and versatile induction method to characterize superconducting samples with planar symmetry, in particular high-T(c) materials, is presented. Specimens can be thin films, thick tapes, ceramic discs, plate-like single crystals, or any other material having two-dimensional geometry and surfaces as small as 10 mm2. Small sized primary and secondary coils are wound around soft ferrite cores, with the sample sandwiched in between. Lock-in detection techniques are used, and both the real chi' and imaginary chi" components of the AC susceptibility are recorded. This yields reliable information on the quality, homogeneity, crystallization and current carrying capacity of the sample, and thus makes a good complement to the resistive characterization of superconductors. In addition, this non-destructive and contactless method allows further annealing on the same specimen in order to compare and improve its superconducting properties. The performance of such a system is given as a function of the thickness and surface of the samples, as well as their response to the AC field.