XPS and Mössbauer studies of amorphous FeGe

Photoemission spectra of amorphous FexGe1-x thin films prepared by thermal evaporation have been studied in situ with a XPS/Auger spectrometer. The composition varied within the range of 0≤x≤0.76 and the degree of surface contamination was monitored by Auger spectroscopy. The binding energies of Ge 3p and 3d as well as the Fe 3p transitions were found to be essentially independent of the alloy composition. Furthermore, no significant difference between the spectra of the alloys and the pure metallic elements could be detected. The results on a crystalline β-FeGe film (∼Fe 3Ge2) were close to the data obtained on amorphous films. Mössbauer spectroscopy measurements down to 4.2 K performed on Fe 0.53Ge0.47 indicated a mixed magnetic state composed of a nonmagnetically ordered doublet and a magnetically ordered broad six-line contribution, whereas the spectra of Fe0.30Ge0.70 showed only a nonmagnetically ordered doublet. By combining our results with published data, we are lead to the conclusion that a charge transfer model is not applicable to these alloys.