Magnetic behavior of probe layers of 57Fe in thin Fe films observed by means of nuclear resonant, scattering of synchrotron radiation

The magnetic behavior of epitaxial probe layers of Fe-57 down to a thickness of 1 monolayer (ML) has been investigated with the technique of nuclear resonant scattering by synchrotron radiation (NRS) in a grazing: incidence geometry. The samples consisted of 10-55 ML Fe deposited onto a Ge(100) substrate and covered with 2 nm Au. Probe layers of 1-10 ML Fe-57 were inserted at different depths in the Fe film. The technique yields spectroscopic information, i.e., magnetic hyperfine fields and isomer shifts, as well as structural information, such as layer thicknesses and interface roughness. The results show the existence of a nonmagnetic Ge/Fe interlayer of at least 10 ML thick after deposition at room temperature. Subsequent conversion electron Mossbauer spectroscopy (CEMS) data show that, although the samples were stored at room temperature, the interlayer diffusion proceeds as a function of time. The relative merits of NRS and CEMS for the investigation of ultrathin layers are discussed.