Magneto-Optical Kerr Rotation Spectra for Fe and TbFe Films on (Cu/SiO2) Multilayered Films

The wavelength dependences of the magnetooptic Kerr rotation angle (¿K) and reflectivity (R) of thin Fe and TbFe films on top of (Cu/SiO2) multilayer films have been measured in the wavelength region from 400 to 900 nm. The onset wavelength at which the reflectivity of (Cu/SiO2) multilayer films begins to increase shifts toward longer wavelengths starting from the absorption edge of Cu as the SiO2 layer thickness is increased. The ¿k of Fe and TbFe films on top of these (Cu/SiO2) multilayer films is enhanced by more than a factor of three at the onset wavelength for these multilayer films, while reflectivities take on minima. The figure of merit ¿R ¿k of these films, reaches twice the value of bulk metals at the ¿K peak wavelength. The calculated ¿R ¿k of Fe and TbFe/ (Cu/SiO2) using the optical constants of Fe, TbFe, Cu and SiO2 and taking optical interference into consideration, agrees with experimental results. With proper choice of the thickness of Cu and SiO2, the figure of merit ¿R ¿k can be enhanced at any wavelength.