Non-monotonic behaviour of the superconducting order parameter in Nb/PdNi bilayers observed through point contact spectroscopy

TL;DR

This study investigates how the superconducting order parameter in Nb/PdNi bilayers varies non-monotonically with ferromagnetic layer thickness, using point contact spectroscopy to reveal damped oscillations in the induced superconducting gap.

Contribution

It provides experimental evidence of non-monotonic behaviour of the superconducting order parameter in Nb/PdNi bilayers through detailed spectroscopy measurements.

Findings

Superconducting gap features observed in dV/dI curves.

Non-monotonic variation of features with PdNi thickness.

Damped oscillatory behaviour of the order parameter in the ferromagnet.

Abstract

Point contact spectroscopy measurements have been performed on Nb/PdNi bilayers in which the thickness of the Nb layer, dNb, was kept constant to 40 nm while the thickness of PdNi, dPdNi, was changed from 2 nm to 9 nm. Features related to the superconducting gap induced in the ferromagnet have been observed in the dV/dI versus V curves. These structures show a non-monotonic behaviour as a function of dPdNi as a consequence of the damped oscillatory behaviour of the superconducting order parameter in the ferromagnetic layer.