Capping effects of Au on Fe/GaAs(001) studied by magneto-optical Kerr effect

Molecular beam epitaxially grown Fe on GaAs(001) capped by Au overlayer with variable thickness had been investigated in situ by magneto-optical Kerr effect (MOKE). It is observed that the MOKE intensity as a function of Au film thickness decays much faster than that derived from the well-known Zak's theory. This can be explained by different optical parameters of ultrathin films from bulk values. It is also found that a minimum thickness of 1.4 nm Au is needed to effectively prevent the oxidation of Fe film at 300 K in atmosphere.