Brillouin light scattering is a powerful technique to measure microwave excitations present in a magnetic system. In microfocused mode, the light is focused on the sample using a microscope objective. This substantially accelerates the measurement but results in mixing the response of all microwave excitations into a single spectrum, such that modeling is required to disentangle the contribution of each spin wave. By assuming that a spectrum collected in microfocused mode can be approximated as the sum of all back-scattering spectra that can be collected by the microscope objective, we develop a simple and direct way of interpreting spectra. The model is compared to experimental data collected on a 50-nm-thick CoFeB magnetic film. The model allows an understanding of the influence of the optical properties of a sample, of the dispersion relation of the spin wave eigenexcitations, and of their thickness profiles, as well as of their populations onto the magnitudes and the line shapes of the characteristic features of a spectrum.

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• Magnetism
• Magneto-optics
• Magnons
• Spintronics
• Spin wave spectroscopy