Thickness dependence of magneto-optic effects in terbium-iron films

Reflectivity, polar Kerr rotation, and magneto-optical (M-o) response of rf-sputtered amorphous TbFe thin films, overcoated with thermally evaporated SiO, were measured as a function of TbFe film thickness in the range 5-150 nm. The optical and M-o properties were found to depend strongly on film thickness and deviations from theoretical calculations were particularly large for very thin films. It was suggested that the complex dielectric tensor, and hence the index of refraction and absorption coefficient, vary with film thickness due to existence of an island-like /void microstructure for very thin films. The importance of an experimental determination of optical and M-O properties in relation to a theoretical computation was pointed out.