  FM1/NM/FM2 trilayers have garnered considerable attention because of their
potential in spintronic applications. A thorough investigation of the spin
transport properties of these trilayers is therefore important. Asymmetric
trilayers, particularly those including Platinum (Pt) as a spacer are less
explored. Pt mediates exchange coupling between the two FM layers and thus
offers a unique platform to investigate the spin-transport properties under
indirect exchange coupling conditions through the spin-pumping mechanism. Our
analytical focus on the acoustic mode of the ferromagnetic resonance spectrum,
facilitated by the distinct magnetizations of the Ni80Fe20 and Co layers,
allows for the isolation of individual layer resonances. The derived
spin-pumping induced damping of the Ni80Fe20 and Co layers reveals a direct
dependence on the Pt spacer thickness. Furthermore, fitting of the weighted
average of the damping parameters to the spin-pumping induced damping of
acoustic mode reveals that the observed FMR spectra is indeed a result of the
in-phase precession of the magnetizations in two FM layers. The extracted
effective spin-mixing conductance varies with the FM/NM interface, specifically
1.72x10^19 m^(-2) at the Ni80Fe20/Pt and 4.07x10^19 m^(-2) at the Co/Pt
interface, indicating a strong correlation with interfacial characteristics.
Additionally, we deduce the spin diffusion length in Pt to be between 1.02 and
1.55 nm and calculate the interfacial spin transparency and spin current
densities, highlighting significant disparities between the Ni80Fe20/Pt and
Co/Pt interfaces. This detailed analysis enhances our understanding of spin
transport in Ni80Fe20/Pt/Co trilayers. It offers insights important for
advancing spintronic device design and lays the groundwork for future
theoretical investigations of trilayer system.
