Interplay between spin-relaxation and Andreev reflection in ferromagnetic wires with superconducting contacts

TL;DR

This paper investigates how superconductivity affects resistance and spin dynamics in ferromagnetic wires with superconducting contacts, highlighting the role of Andreev reflection and spin relaxation.

Contribution

It provides a detailed analysis of resistance changes due to Andreev scattering and spin relaxation effects at ferromagnet-superconductor interfaces.

Findings

Superconductivity induces additional contact resistance.

Double Andreev scattering leads to internal reflection of spin-polarized electrons.

Resistance change is comparable to the ferromagnetic wire's spin-relaxation length.

Abstract

We analyze the change in the resistance of a junction between a diffusive ferromagnetic (F) wire and normal metal electrode, due to the onset of superconductivity (S) in the latter and a double Andreev scattering process leading to a complete internal reflection of a large fraction of the spin-polarized electrons back into the ferromagnet. The superconducting transition results in an additional contact resistance arising from the necessity to match spin-polarized current in F-wire to spin-less current in S-reservoir, which is comparable to the resistance of a piece of a F-wire with the length equal to the spin-relaxation length.