Characterization of superconducting nanometric multilayer samples for superconducting rf applications: First evidence of magnetic screening effect

for the preparation of superconducting electronics circuits. The samples were characterized by x-ray reflectivity, dc resistivity (PPMS), and dc magnetization (SQUID) measurements. Dc magnetization curves of a 250 nm thick Nb film have been measured, with and without a magnetron sputtered coating of a single or multiple stack of 15 nm MgO and 25 nm NbN layers. The Nb samples with/without the coating exhibit different behaviors and clearly show an enhancement of the magnetic penetration field. Because SQUID measurements are influenced by edge and shape effects, we propose to develop a specific local magnetic measurement of HC1 based on ac third harmonic analysis in order to reveal the true screening effect of multilayers.