Structural, magnetic and superconducting characterization of the CuNi/Nb bilayers of the S/F type using Polarized Neutron Reflectometry and complementary techniques

TL;DR

This study comprehensively characterizes Nb/CuNi bilayers, revealing high-quality interfaces, superconducting transition temperatures, and ferromagnetic properties using polarized neutron reflectometry and complementary techniques.

Contribution

It provides detailed structural, magnetic, and superconducting insights into Nb/CuNi bilayers, including interface quality and magnetic behavior, using polarized neutron reflectometry and other methods.

Findings

Interface roughness does not exceed 1 nm.

Superconducting transition temperatures align with literature.

Superconducting layer has a screening length of 120 nm.

Abstract

Structural, magnetic, and superconducting properties of S/F bilayers Nb/Cu40Ni60 deposited on silicon substrate have been characterized using Polarized Neutron Reflectometry and complementary techniques. The study allowed to determine real thicknesses of the S and F layers as well as the r.m.s. roughness of the S/F interfaces. The latter does not exceed 1 nm, showing the high quality of the S/F interface. Using SQUID and a mutual inductance setup we determined the superconducting transition temperatures of the samples, which are in agreement with the literature data. Using of PNR for the single S layer allowed to determine the screening length lambda of the superconducting layer, lambda = 120 nm. This value is higher than the London penetration depth for pure niobium which may indicate that the superconductor is in the dirty limit. PNR and SQUID studies of magnetic properties of the CuNi layer have shown the presence of ferromagnetism in all investigated samples.