Proximity and Josephson effects in superconductor - antiferromagnetic Nb / \gamma-Fe50Mn50 heterostructures

TL;DR

This study investigates the proximity and Josephson effects in superconductor-antiferromagnetic heterostructures, specifically Nb/b3-FeMn50, measuring critical current scaling and coherence lengths, and fabricating the first trilayer Josephson junctions with these materials.

Contribution

First fabrication and measurement of superconductor-antiferromagnetic-superconductor Josephson junctions using Nb and b3-FeMn50, revealing key coherence lengths and electronic properties.

Findings

Coherence length in AF is 2.4 nm.

Diffusion constant for FeMn is 1.7 7^{-4} m^2/s.

Confirmed AF nature of FeMn via exchange biased bilayers.

Abstract

We study the proximity effect in superconductor (S), antiferromagnetic (AF) bilayers, and report the fabrication and measurement of the first trilayer S/AF/S Josephson junctions. The disordered f.c.c. alloy \gamma-Fe50Mn50 was used as the AF, and the S is Nb. Micron and sub-micron scale junctions were measured, and the scaling of $J_C (d_AF)$ gives a coherence length in the AF of 2.4 nm, which correlates with the coherence length due to suppression of $T_C$ in the bilayer samples. The diffusion constant for FeMn was found to be 1.7 \times 10$^{-4}$ m$^2$ s$^-1$, and the density of states at the Fermi level was also obtained. An exchange biased FeMn/Co bilayer confirms the AF nature of the FeMn in this thickness regime.