Spin Transport and Magnetic Proximity Effect in CoFeB/Normal Metal/Pt Trilayers

We present a study of the damping and spin pumping properties of CoFeB/X/Pt systems with
$\rm X=Al,Cr$
, and
$\rm Ta$
. We show that the total damping of the CoFeB/Pt systems is strongly reduced when an interlayer is introduced independently of the material. Using a model that considers spin relaxation, we identify the origin of this contribution in the magnetically polarized Pt formed by the magnetic proximity effect (MPE), which is suppressed by the introduction of the interlayer. The induced ferromagnetic order in the Pt layer is confirmed by element-sensitive transverse magneto-optical Kerr spectroscopy at the M
$_{2,3}$
and N
$_{7}$
absorption edges. We discuss the impact of the MPE on parameter extraction in the spin transport model.