Setup of a new BLS apparatus with submicrometric lateral resolution and its application to the study of spin modes in nanomagnets

A new microfocused Brillouin light scattering BLS apparatus has been setup using a microscope objective with large numerical aperture and achieving a submicrometric lateral resolution, as inferred by reflectivity measurements taken on a set of calibration arrays consisting of Al stripes with different spacings. The micro-BLS apparatus has been then used to investigate the magnetic normal modes of elliptical Permalloy nanorings. The superiority of micro-BLS over conventional BLS measurements in the detection of stationary modes, especially those localized close to the edges of the nanoring where the internal field is highly nonhomogeneous, is demonstrated. A satisfactory interpretation of the measured spectra in terms of dynamical magnetization distribution inside the rings was achieved by a comparison with the output of dynamical micromagnetic simulations.