Study of spin pumping in Co thin film vis-a-vis seed and capping layer using ferromagnetic resonance spectroscopy

TL;DR

This study examines how seed and capping layers influence spin pumping in 3 nm Co thin films using ferromagnetic resonance spectroscopy, revealing layer-dependent damping and spin conductance effects.

Contribution

It provides new insights into the impact of different seed and capping layers on spin pumping and damping in ultrathin Co films, with quantitative analysis of spin conductance.

Findings

Damping constant varies significantly with layer composition.

Pt layers increase damping due to high spin orbit coupling.

Effective spin conductance measured at 2.0e18 m-2 in trilayer structures.

Abstract

We investigated the dependence of the seed [Ta/Pt, Ta/Au] and capping [Pt/Ta, Au/Ta] layers on spin pumping effect in the ferromagnetic 3 nm thick Co thin film using ferromagnetic resonance spectroscopy. The data is fitted with Kittel equation to evaluate damping constant and g-factor. A strong dependence of seed and capping layers on spin pumping has been discussed. The value of damping constant {alpha} is found to be relatively large i.e. 0.0326 for the Ta{3}/Pt{3}/Co{3}/Pt{3}/Ta{3} {nm} multi-layer structure, while it is 0.0104 for Ta{3}/Co{3}/Ta{3} {nm}. Increase in {alpha} is observed due to Pt layer that works as a good sink for spins due to high spin orbit coupling. In addition, we measured the effective spin conductance = 2.0e18 m-2 for the trilayer structure Pt{3}/Co{3}/Pt{3} {nm} as a result of the enhancement in {alpha} relative to its bulk value. We observed that the evaluated g-factor decreases as effective demagnetizing magnetic field increases in all the studied samples. The azimuthal dependence of magnetic resonance field and line width showed relatively high anisotropy in the trilayer Ta{3}/Co{3}/Ta{3} {nm} structure.