Radiative damping in wave guide based FMR measured via analysis of perpendicular standing spin waves in sputtered Permalloy films

TL;DR

This paper investigates the radiative damping in Permalloy films using VNA-FMR by analyzing perpendicular standing spin waves, identifying three main damping contributions, and proposing a method to measure radiative damping from a single resonance.

Contribution

It introduces a simple analytical model to quantify radiative damping and demonstrates how to determine it from single-resonance FMR measurements.

Findings

Radiative damping significantly contributes to total damping in Permalloy films.

The damping can be fully explained by intrinsic, eddy-current, and radiative contributions.

A new method to measure radiative damping from a single resonance is proposed.

Abstract

The damping $\alpha$ of the spinwave resonances in 75 nm, 120 nm, and 200nm -thick Permalloy films is measured via vector-network-analyzer ferromagnetic-resonance (VNA-FMR) in the out-of-plane geometry. Inductive coupling between the sample and the waveguide leads to an additional radiative damping term. The radiative contribution to the over-all damping is determined by measuring perpendicular standing spin waves (PSSWs) in the Permalloy films, and the results are compared to a simple analytical model. The damping of the PSSWs can be fully explained by three contributions to the damping: The intrinsic damping, the eddy-current damping, and the radiative damping. No other contributions were observed. Furthermore, a method to determine the radiative damping in FMR measurements with a single resonance is suggested.