Thickness-dependent oscillation of the magneto-optical properties of Au-sandwiched (001) Fe films

Au-sandwiched bcc (001) Fe wedges were produced by the molecular beam epitaxy method (0–20 Å). The polar Kerr rotation and Kerr ellipticity spectra (1.5–5 eV) were measured as a function of the Fe thickness d. In both kinds of spectra new peaks appear. The complex Kerr rotation oscillates as a function of the film thickness. More than four oscillations could be clearly observed in the measured thickness range. Magneto-optical transitions from the ${\mathrm{\Delta }}_5$ band to quantum-well states (QWS’s) in the ${\mathrm{\Delta }}_1$ majority-spin band change the intrinsic dielectric properties. The oscillation period and transition energies are in agreement with theory. Thickness-dependent structures below 2.5 eV strongly suggest the occurrence of partially confined QWS’s around ${\mathit{E}}_{\mathit{F}}$ or QWS’s in the ${\mathrm{\Delta }}_5$ band.