0-pi oscillations in nanostructured Nb/Fe/Nb Josephson junctions

TL;DR

This study explores 0-$$ oscillations in Nb/Fe/Nb Josephson junctions, revealing how Fe barrier thickness influences the transition between 0 and $$ states, with implications for spintronics and quantum computing.

Contribution

It provides experimental data and theoretical analysis of 0-$$ phase transitions in Nb/Fe/Nb junctions, including estimates of key magnetic and electronic parameters.

Findings

Fe barrier thickness causes 0-$$ state oscillations.

Decay rate of $I_CR_N$ shows nonmonotonic oscillatory behavior.

Estimated exchange energy and Fermi velocity align with previous reports.

Abstract

The physics of the $\pi$ phase shift in ferromagnetic Josephson junctions may enable a range of applications for spin-electronic devices and quantum computing. We investigate transitions from ``0'' to ``$\pi$'' states in Nb/Fe/Nb Josephson junctions by varying the Fe barrier thickness from 0.5 nm to 5.5 nm. From magnetic measurements we estimate for Fe a magnetic dead layer of about 1.1 nm. By fitting the characteristic voltage oscillations with existing theoretical models we extrapolate an exchange energy of 256 meV, a Fermi velocity of $1.98 \times 10^5$ m/s and an electron mean free path of 6.2 nm, in agreement with other reported values. From the temperature dependence of the $I_CR_N$ product we show that its decay rate exhibits a nonmonotonic oscillatory behavior with the Fe barrier thickness.