Depairing currents in superconductor / ferromagnet Nb/CuNi trilayers close to T$_c$

TL;DR

This study investigates how the magnetic state of ferromagnetic layers influences the superconducting current in Nb/CuNi trilayers near the critical temperature, revealing a link between magnetization and superconductivity suppression.

Contribution

It introduces a pulsed-current measurement method to analyze the impact of ferromagnetic domain states on superconducting depairing currents in S/F/S trilayers.

Findings

Depairing current correlates with magnetization behavior.

Superconductivity suppression is minimized at the ferromagnetic coercive field.

Magnetic domain states significantly influence superconducting properties.

Abstract

In superconductor/ferromagnet (S/F) heterostructures, the exchange field $h_{ex}$ of the F-layer suppresses the superconducting order parameter in the S-layer via the proximity effect. One issue in current research is the effect of a domain state, or, more generally, different directions of $h_{ex}$, on the superconductivity. We used a pulsed-current technique in order to measure the superconducting transport properties of Cu$_{1-x}$Ni$_x$/Nb/Cu$_{1-x}$Ni$_x$ ($x$ = 0.54) F/S/F trilayers structured in strips of about 2 $\mu$m wide and 20 $\mu$m long as function of a small in-plane magnetic field. We find that the depairing current is tied to the magnetization behavior. In particular, we show that the suppression of superconductivity in the S-layer is smallest when the external magnetic field equals the coercive field H$_{c}$ of the F-layers.