Critical Current Behavior in Josephson Junctions with the Weak Ferromagnet PdNi

TL;DR

This study investigates how the critical current in superconductor/ferromagnet/superconductor Josephson junctions varies with PdNi ferromagnet thickness, revealing oscillations and decay without evidence of long-range triplet correlations.

Contribution

It provides detailed measurements of critical current oscillations and decay in S/F/S junctions with PdNi, highlighting the absence of long-range triplet effects and discussing potential causes.

Findings

Critical current oscillates with a period of ~13 nm.

Critical current density decreases by five orders of magnitude over studied thickness.

No evidence of long-range spin-triplet pair correlations was observed.

Abstract

We have studied the variation of critical current in Superconductor/Ferromagnet/Superconductor (S/F/S) Josephson Junctions as a function of ferromagnet thickness using a weakly-ferromagnetic alloy Pd82Ni12. Measurements were performed for the thickness range 32 to 100 nm, over which the critical current density decreases by five orders of magnitude. The critical current density oscillates with a period of 12.9 +/- 0.3 nm, and decays over a characteristic length of 8.0 +/- 0.5 nm. There is no evidence of a crossover to a slower decay, which might indicate the presence of long-range spin-triplet pair correlations. We discuss possible reasons for their absence, including the possibility of strong spin flip scattering in PdNi.