Magneto-optical signal from Co 2 Mn-based Heusler thin films in MOKE and BLS

Abstract Co 2 Mn-based Heusler compounds offer a versatile, composition-tunable platform for magnonics and spintronics. Among them, the half-metallic Co 2 MnSi is of particular interest for magnonics owing to its ultralow Gilbert damping, yet its weak magneto-optical response in the visible challenges optical probing such as Brillouin light scattering (BLS). We study the magneto-optical response of epitaxial Co 2 Mn X films ( X = {Al x Si 1-x , Ga x Ge 1-x , Sn}) by magneto-optical Kerr effect (MOKE) spectroscopy and BLS. Angle-resolved MOKE resolves a significant, wavelength-dependent quadratic MOKE (QMOKE) only for Co 2 MnSi, whereas Co 2 MnAl, Co 2 MnGa and Co 2 MnSn respond dominantly linearly. Comparing BLS intensities of thermal magnons at two wavelengths, Co 2 MnSi gives the weakest signal at 532 nm yet among the strongest at 457 nm, tracking the spectral dependence of its Kerr angle. These results emphasise the relation between the two magneto-optical techniques, guiding the choice of probing wavelength for Co 2 Mn-based Heusler compounds, and provide a transferable approach for other magnetic materials.