  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.
