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

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 10nm−2. The experimental quantification of these spin transport parameters is an important step towards the development of superconducting spintronic devices involving NbN thin films.