Controllable Josephson current through a pseudo-spin-valve structure

TL;DR

This paper demonstrates control over the Josephson critical current in a superconductor/ferromagnet hybrid structure using a pseudo-spin-valve, showing correlated modulation of resistance and current with magnetic field at 4.2 K.

Contribution

It introduces a pseudo-spin-valve structure integrated with superconducting contacts to controllably modulate Josephson current via magnetic field cycling.

Findings

Josephson critical current observed at 4.2 K.

Magnetoresistance of approximately 0.5%.

Modulation of $I_C$ correlates with MR hysteresis loops.

Abstract

A thin Co/Cu/Permalloy (Ni$_{80}$Fe$_{20}$) pseudo-spin-valve structure is sandwiched between superconducting Nb contacts. When the current is passed perpendicular to the plane of the film a Josephson critical current ($I_C$) is observed at 4.2 K, in addition to a magnetoresistance (MR) of $\sim$ 0.5 % at high bias. The hysteresis loop of the spin-valve structure can be cycled to modulate the zero field $I_C$ of the junction in line with the MR measurements. These modulations of resistance and $I_C$ occur both smoothly and sharply with the applied field. For each type of behaviour there is a strong correlation between shape of the MR loops and the $I_C$ modulation.