Plasmon-enhanced Brillouin Light Scattering spectroscopy for magnetic systems. I. Theoretical Model

TL;DR

This paper develops a theoretical model for plasmon-enhanced Brillouin light scattering spectroscopy, aiming to improve detection sensitivity and range for spin waves in magnetic nanostructures by optimizing nanoparticle configurations.

Contribution

It introduces a generalized theoretical framework for plasmon-enhanced BLS spectroscopy considering various nanoparticle geometries and provides analytical insights into key parameters affecting enhancement.

Findings

The height-to-radius ratio of plasmon resonators significantly influences BLS enhancement.

Effective susceptibilities are calculated using electrodynamic Green functions.

The model guides numerical design of nanoparticle morphology for optimal BLS sensitivity.

Abstract

Brillouin light scattering (BLS) spectroscopy is an effective method for detecting spin waves in magnetic thin films and nanostructures. While it provides extensive insight into the properties of spin waves, BLS spectroscopy is impeded in many practical cases by the limited range of detectable spin wave wavenumbers and its low sensitivity. Here, we present a generalized theoretical model describing plasmon-enhanced BLS spectroscopy. Three types of plasmonic nanoparticles in the shape of an ellipsoid of rotation are considered: a single plasmon resonator, a sandwiched plasmonic structure in which two nanoparticles are separated by a dielectric spacer, and an ensemble of metallic nanoparticles on the surface of a magnetic film. The effective susceptibilities for the plasmonic systems at the surface of the magnetic film are calculated using the electrodynamic Green functions method, and the enhancement coefficient is defined. It is analytically shown that the ratio of the plasmon resonator height to its radius plays the key role in the development of plasmon-enhanced BLS spectroscopy. The developed model serves as a basis for numerical engineering of the optimized plasmon nanoparticle morphology for BLS enhancement.