Enhanced superconducting proximity effect in clean ferromagnetic domain structures

TL;DR

This paper studies how superconducting correlations penetrate into a clean ferromagnetic structure with two antiparallel domains, revealing an enhanced proximity effect due to exchange field cancellation, with implications for superconducting spintronics.

Contribution

It demonstrates that antiparallel ferromagnetic domains can enhance the superconducting proximity effect compared to single domain structures, due to exchange field cancellation effects.

Findings

Enhanced superconducting correlations in antiparallel domains.

Oscillatory behavior of pair amplitude with domain thickness.

Proximity density of states oscillations grow with second domain's thickness.

Abstract

We investigate the superconducting proximity effect in a clean magnetic structure consisting of two ferromagnetic layered domains with antiparallel magnetizations in contact with a superconductor. Within the quasiclassical Green's function approach we find that the penetration of the superconducting correlations into the magnetic domains can be enhanced as compared to the corresponding single domain structure. This enhancement depends on an effective exchange field which is determined by the thicknesses and the exchange fields of the two domains. The pair amplitude function oscillates spatially inside each domain with a period inversely proportional to the local exchange field. While the oscillations have a decreasing amplitude with distance inside the domain which is attached to the superconductor, they are enhancing in the other domain and can reach the corresponding normal metal value for a zero effective exchange field. We also find that the corresponding oscillations in the Fermi level proximity density of states as a function of the second domain's thickness has an growing amplitude over a range which depends on the effective exchange field. Our findings can be explained as the result of cancellation of the exchange fields induced phases gained by an electron inside the two domains with antiparallel magnetizations.