Simultaneous measurement of the electrical and magnetic properties of a superconductive plate sample with a bifilar coil

In order to simultaneously evaluate the resistivity (ρ) and the magnetic penetration depth (λ) of a flat plate superconductor, a method using a bifilar winding coil is proposed. The bifilar winding coil, which has the same properties, consists of two coils located at same place. When a current is applied in the same or opposite direction with the sample fixed, the magnetic fluxes augment or counteract each other. The difference in the synthetic impedance of the two coils in the above cases corresponds to the cases when there is a sample or no sample in the conventional method (SRPM method). This difference is compared with the values calculated for ρ and λ as parameters to estimate the experimental values of ρ and λ. For a Bi pellet superconductor, ρ and λ were simultaneously estimated at 10 kHz. The values of ρ and λ at 77.3 K was 4.2×^-11 Ωm and 20.4 μm, respectively. This method, which does not electrically touch the sample, is superior to the conventional method for measuring very low resistivity