Antiferromagnetic NiO thickness dependent sign of the spin Hall magnetoresistance in -FeO/NiO/Pt epitaxial stacks

Dong, B.-W.*; Baldrati, L.*; Schneider, C.*; Niizeki, Tomohiko*; Ramos, R.*; Ross, A.*; Cramer, J.*; Saito, Eiji; Klui, M.*

We study the spin Hall magnetoresistance (SMR) in epitaxial -FeO/NiO(001)/Pt stacks, as a function of temperature and thickness of the antiferromagnetic insulating NiO layer. Upon increasing the thickness of NiO from 0 nm to 10 nm, we detect a sign change of the SMR in the temperature range between 10 K and 280 K. This temperature dependence of the SMR in our stacks is different compared to that of previously studied yttrium iron garnet/NiO/Pt, as we do not find any peak or sign change as a function of temperature. We explain our data by a combination of spin current reflection from both the NiO/Pt and -FeO/NiO interfaces and the thickness-dependent exchange coupling mode between the NiO and -FeO layers, comprising parallel alignment for thin NiO and perpendicular alignment for thick NiO.