Superconducting properties of Nb/Pb/Nb trilayer

Fabrication of superconducting layered systems offers fascinating possibilities to observe novel superconducting phenomena. In this work we study a new nanostructured superconducting trilayer. Nb/Pb/Nb trilayer was grown by magnetron sputtering and the superconducting properties were studied via magnetic and electrical transport measurements. The magnetization and resistivity have been analyzed as functions of the temperature and magnetic field applied perpendicularly to the layers. The sample presents sharp resistive and magnetic transitions at T_C = 7.2 K. Vortex avalanches attributed to thermomagnetic instabilities were observed in magnetization versus applied field loops. The temperature dependence of μ₀Hc₂ presents a positive upward curvature at low temperatures, indicating a crossover which is consistent with the Takahashi–Tachiki model for superconducting superlattices. The temperature dependence of the lower critical field μ₀Hc₁(T) presents an unconventional feature consistent with a multicomponent behavior with spatially separated components. (paper)