Theory of Brillouin Light Scattering from Ferromagnetic Nanospheres

TL;DR

This paper develops a theoretical framework for Brillouin light scattering from spin wave modes in ferromagnetic nanospheres, enabling calculation of scattering spectra and intensities based on eigenmodes.

Contribution

It introduces a comprehensive theory incorporating optical field variation and eigenvector normalization for accurate BLS spectrum predictions in ferromagnetic nanospheres.

Findings

Calculated BLS spectra for dipole/exchange spin wave modes.

Identified relative intensities of different spin wave modes.

Provided a method for absolute cross section calculation.

Abstract

We develop the theory of Brillouin light scattering (BLS) from spin wave modes in ferromagnetic nanospheres, within a framework that incorporates the spatial variation of the optical fields within the sphere. Our recent theory of exchange dipole spin wave modes of the sphere provides us with eigenvectors. When properly normalized, these eigenvectors allow calculation of the absolute cross section of various modes which contribute to BLS spectrum. We then present explicit calculation of the BLS spectrum associated with the first few dipole/exchange spin wave modes with emphasis on their relative intensity.