Spin transport parameters of NbN thin films characterised by spin pumping experiments

TL;DR

This study measures spin transport parameters in NbN thin films using spin pumping and inverse spin-Hall effect experiments, providing key data for superconducting spintronics development.

Contribution

It introduces a method to quantify spin diffusion length, spin Hall angle, and interface conductance in NbN thin films through experimental and theoretical analysis.

Findings

Spin diffusion length in NbN is 14 nm.

Spin Hall angle in NbN is -1.1×10^-2.

Spin-mixing conductance at NbN/YIG interface is 10 nm^-2.

Abstract

We present measurements of ferromagnetic-resonance - driven spin pumping and inverse spin-Hall effect in NbN/Y3Fe5O12 (YIG) bilayers. A clear enhancement of the (effective) Gilbert damping constant of the thin-film YIG was observed due to the presence of the NbN spin sink. By varying the NbN thickness and employing spin-diffusion theory, we have estimated the room temperature values of the spin diffusion length and the spin Hall angle in NbN to be 14 nm and -1.1 10-2, respectively. Furthermore, we have determined the spin-mixing conductance of the NbN/YIG interface to be 10 nm-2. The experimental quantification of these spin transport parameters is an important step towards the development of superconducting spintronic devices involving NbN thin films.