We investigated the spin pumping damping contributed by paramagnetic layers (Pd, Pt) in both direct and indirect contact with ferromagnetic Ni81Fe19 films. We find a nearly linear dependence of the interface-related Gilbert damping enhancement Δα on the heavy-metal spin-sink layer thicknesses tN in direct-contact Ni81Fe19/(Pd, Pt) junctions, whereas an exponential dependence is observed when Ni81Fe19 and (Pd, Pt) are separated by \unit[3]{nm} Cu. We attribute the quasi-linear thickness dependence to the presence of induced moments in Pt, Pd near the interface with Ni81Fe19, quantified using X-ray magnetic circular dichroism (XMCD) measurements. Our results show that the scattering of pure spin current is configuration-dependent in these systems and cannot be described by a single characteristic length.
@article{arxiv.1308.0450,
title = {Spin pumping damping and magnetic proximity effect in Pd and Pt spin-sink layers},
author = {M. Caminale and A. Ghosh and S. Auffret and U. Ebels and K. Ollefs and F. Wilhelm and A. Rogalev and W. E. Bailey},
journal= {arXiv preprint arXiv:1308.0450},
year = {2016}
}