Penetration depth measurements for Nd 1.85Ce 0.15CuO 4 and NbCN thin films using a kinetic inductance technique

Abstract

The absolute value and the temperature dependence of the magnetic penetration depth λ( T) have been measured for high-quality NbCN and Nd 1.85Ce 0.15CuO 4 (NCCO) thin films. A kinetic inductance technique was used to measure the screening of a thin superconducting film where the film thickness d was less than or of the order of the London penetration depth. In this limit the kinetic inductance L k is proportional to λ 2( T)/ d. The kinetic inductance was measured on unpatterned films using a two-coil mutual inductance technique. It was found that the temperature dependence of the penetration depth for NbCN and NCCO at low temperatures is exponential as expected, confirming earlier reports. We also describe how λ(0) can be extracted from the kinetic inductance data.