Magnetic relaxation in bilayers of yttrium iron garnet/platinum due to the dynamic coupling at the interface

TL;DR

This paper investigates how dynamic coupling at the interface of yttrium iron garnet/platinum bilayers causes additional magnetic relaxation, explaining large ferromagnetic resonance broadening in thick films due to interface effects.

Contribution

It introduces a new mechanism of magnetic relaxation transfer via dynamic coupling at the FM/NM interface, independent of FM film thickness.

Findings

Dynamic coupling transfers magnetic relaxation from conduction electrons to FM spins.

Relaxation due to dynamic coupling is independent of FM film thickness.

Explains large ferromagnetic resonance broadening in thick YIG/Pt films.

Abstract

We show that in ferromagnetic (FM)/normal metal (NM) bilayers the dynamic coupling at the interface transfers an additional magnetic relaxation from the heavily damped motion of the conduction electron spins in the NM layer to the FM spins. While the FM relaxation rates due to two-magnon scattering and spin pumping decrease rapidly with increasing FM film thickness, the damping due to the dynamic coupling does not depend on the FM film thickness. The proposed mechanism explains the very large broadening of ferromagnetic resonance lines in thick films of yttrium iron garnet after deposition of a Pt layer.