Optical determination of the exchange stiffness constant in an iron garnet

TL;DR

This paper presents a novel optical method using Brillouin light scattering to measure the exchange stiffness constant in an iron garnet, providing a new way to characterize magnetic materials.

Contribution

The study introduces a method to estimate the exchange stiffness constant from backscattering magnon mode frequencies in iron garnets.

Findings

Exchange stiffness constant measured aligns with previous values for similar materials.

Backscattering magnon mode identified as a key feature for optical measurement.

Method offers a non-invasive way to determine magnetic exchange properties.

Abstract

Brillouin light scattering measurements were performed in the backscattering geometry on a Bi-substituted rare earth iron garnet. We observed two different peaks, one attributed to a surface spin wave in the dipole-exchange regime. The other is referred to as a backscattering magnon mode, because the incident light in this case is scattered backward by exchange-dominated spin wave inside the material. We propose a method to estimate the exchange stiffness constant from the frequency of the backscattering magnon mode. The obtained value is comparable with the previously reported values for Y$ _3 $Fe$ _5 $O$ _{12} $.