We investigated interlayer exchange coupling through Pt/Ru/Pt and Pt/Ru multilayers as candidates of nonmagnetic spacer layers in the synthetic antiferromagnetic (AF) layer, which is available for studying AF spintronics using current-induced spin-orbit torque (SOT) switching originating from the spin Hall effect. The AF interlayer exchange coupling with the oscillation period of Λ2 ∼ 1.05 nm was observed even for the face-centered cubic (fcc) Pt (tPt)/hexagonal Ru/fcc Pt (tPt) nonmagnetic spacer layer structures in the wide range of both Pt and total nonmagnetic spacer layer thicknesses (0 ≤ tPt ≤ 0.8 nm, 1.0 ≤ ttotal ≤ 2.3 nm), which would be useful for the systematic investigation of the SOT on the AF structure. Moreover, we observed the disappearance of the one oscillation period (Λ1 ∼ 1.65 nm) in the case of Pt(111)/Ru(0001) and Pt(111)/Ru(0001)/Pt(111) spacer layers, whereas the existence of two oscillation periods of AF interlayer exchange coupling (Λ1 ∼ 1.65 nm and Λ2 ∼ 1.05 nm) in the case of Ru spacer layer was observed. We expect that the Pt/Ru/Pt spacer layer with the oscillation period of Λ2 ∼ 1.05 nm will pave a way to the AF spintronics based on the multilayer systems.
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