Nb/CuNi Sandwiches as Superconducting Spin-Valve Core Structures

TL;DR

This study investigates CuNi/Nb/CuNi trilayers used as superconducting spin-valve cores, analyzing how magnetic configurations influence the critical temperature and identifying the fundamental limits imposed by material and interface properties.

Contribution

The paper reproduces the Tc shift in CuNi/Nb/CuNi structures and explores the performance limits dictated by material ratios and interface transparency.

Findings

Tc shift is close to the fundamental material limits.

Main limiting factors are the superconductor thickness ratio and interfacial transparency.

Performance is constrained by intrinsic material properties.

Abstract

We have investigated CuNi/Nb/CuNi trilayers, as have been recently used as the core structure of a spin-valve like device [J. Y. Gu et al., Phys. Rev. Lett. 89, 267001 (2002)] to study the effect of magnetic configurations of the CuNi layers on the critical temperature, Tc, of the superconducting Nb. After reproducing a Tc shift of a few mK, we have gone on to explore the performance limits of the structure. The results showed the Tc shift we found to be quite close to the basic limits of this particular materials system. The ratio between the thickness and the coherence length of the superconductor and the interfacial transparency were the main features limiting the Tc shift.