Guidelines for interpreting microfocused Brillouin light scattering spectra

TL;DR

This paper analyzes how spin wave dispersion and profiles influence microfocused Brillouin Light Scattering spectra across different magnetic materials, providing guidelines for interpreting complex spectral features.

Contribution

It offers a detailed analysis of spectral features based on dispersion relations and mode profiles, enhancing interpretation accuracy for diverse magnetic materials.

Findings

Spectral shapes reflect underlying spin wave dispersion and profiles.

Exact dispersion relations are necessary near mode hybridization.

Analytical expressions suffice when modes are well separated.

Abstract

We present an analysis of the influence of spin wave dispersion relations and profiles on microfocused Brillouin Light Scattering spectra. Three archetypal magnetic materials are reported: a 51-nm thick Bi-substituted YIG, a 25-nm thick Heusler compound and 50-nm thick CoFeB alloy. These samples were chosen because they exhibit strongly contrasting spectral features -peak frequencies, linewidth, skewness. The shapes of these spectral features reflect the underlying spin wave dispersion relations and the thickness profile of the related spin wave modes. While analytical expressions of the dispersion relations provide a satisfactory description of the spectra if the modes are in separate frequency domains, the exact dispersion relations and the exact mode profiles are required for a correct description of the spectra not only when mode hybridization is present in the range or near the range of frequencies and wavevector accessed by the experiment. Our examples of microfocused BLS spectra are handy references that can be used as interpretation guidelines for BLS spectra recorded on a broader range of materials.