Spin transport in antiferromagnetic NiO and magnetoresistance in Y$_3$Fe$_5$O$_{12}$/NiO/Pt structures

TL;DR

This study investigates spin transport and magnetoresistance in YIG/NiO/Pt trilayers, revealing exponential decay of spin signals with NiO thickness and contrasting behaviors of ISHE and SMR responses.

Contribution

It provides the first detailed comparison of spin transport decay and magnetoresistance behavior in NiO-based trilayers, highlighting different length scales for ISHE and SMR.

Findings

ISHE voltage decays exponentially with NiO thickness (decay length ~3.9 nm)

SMR signal drops abruptly around 4 nm NiO thickness

Different length scales govern spin transport and magnetoresistance in NiO layers

Abstract

We have studied spin transport and magnetoresistance in yttrium iron garnet (YIG)/NiO/Pt trilayers with varied NiO thickness. To characterize the spin transport through NiO we excite ferromagnetic resonance in YIG with a microwave frequency magnetic field and detect the voltage associated with the inverse spin-Hall effect (ISHE) in the Pt layer. The ISHE signal is found to decay exponentially with the NiO thickness with a characteristic decay length of 3.9 nm. This is contrasted with the magnetoresistance in these same structures. The symmetry of the magnetoresistive response is consistent with spin-Hall magnetoresistance (SMR). However, in contrast to the ISHE response, as the NiO thickness increases the SMR signal goes towards zero abruptly at a NiO thickness of $\simeq$ 4 nm, highlighting the different length scales associated with the spin-transport in NiO and SMR in such trilayers.