Dimensional crossover and flux pinning of decoupled Cu(50)Ni(50)/Nb multilayers

Abstract

The behaviors of superconducting transition temperature T(c) and upper critical field H(c2) as a function of different superconductor thicknesses have been investigated in Cu(50)Ni(50)/Nb trilayers and multilayers. We deduced superconductor critical thickness, below which superconductivity vanishes, by analyzing the data in terms of proximity theory. The temperature dependence of H(c2) measurement reveals the spatial dimensional crossover and the flux pinning mechanism in the superconductor. A strong pair-breaking effect was observed in the weak ferromagnetic Cu(50)Ni(50) layers from both measurements. We attribute our observation to the high interface transparency between Cu(50)Ni(50) and Nb. (C) 2008 American Institute of Physics.