Electron spectroscopy studies on amorphous GdFe and GdCo alloys

Abstract

I n situ XPS photoelectron studies on amorphous thermally evaporated GdFe and GdCo films have been made under UHV conditions. The results were used to test the conventional concept of charge transfer, which had been applied to the materials under discussion. The XPS binding energies were found to be identical in the pure elements and the alloys, suggesting that the core levels in a-GdFe and a-GdCo are not very sensitive to a change in the chemical environment. Thus, it was concluded that the transfer of charge from Gd to the transition metal d bands, if existing at all, must be smaller than one electron per Gd atom. The preferential oxidation of Gd in GdFe and GdCo films was found to be characteristically reflected in the low-energy transitions of the Auger spectra, which hence were used to distinguish between the clean and the oxidized state of Gd. The influence of oxidation from the Gd 4d and 4f levels was characterized in some separate experiments on pure Gd.

X-ray photoelectron spectroscopy study of MBE-grown Gd/EuTe multilayers

“…As it can be seen from Fig. 3, the strong structure with maximum at 8.4 eV can be attributed to the Gd 4f multiplet [17,19,22]. In this case, when aluminium cap layer has been removed and trivalent europium structure appears in the sample, the weak Eu 3+ 4f multiplet structure is fully screened by gadolinium multiplet (see Fig.…”

“…It is known that gadolinium is highly reactive with oxygen and residual gases [17,19]. Wandelt and Brundle [17] have studied the interaction of oxygen with evaporated Gd films at room temperature by Al K␣ XPS and HeI and HeII UPS techniques.…”

“…The influence of oxidation upon the position and the shape of the Gd 4f and 4d peaks were observed within the interval shorter than 1 h. In this research, the 4d core level region spectra of Gd/EuTe multilayers structure were being recorded ∼2 h after the beginning of the measurements of XPS spectra set. The features of the observed changes in 4d core level spectra can be caused by the interaction of the Gd with ambient gases in XPS chamber [19]. In order to eliminate the influence of the ambient gases on such materials during the photoemission experiment the lower pressure in the analysis chamber or (and) the shorter measuring time is required.…”

“…In the Ref. [19] the changes in the photoemission spectra of Gd, resulting from the exposure to the ambient gases (H 2 , CH x , H 2 O, CO and CO 2 ) at a total pressure of 5.0 × 10 −10 Torr, were monitored as a function of exposure time. The influence of oxidation upon the position and the shape of the Gd 4f and 4d peaks were observed within the interval shorter than 1 h. In this research, the 4d core level region spectra of Gd/EuTe multilayers structure were being recorded ∼2 h after the beginning of the measurements of XPS spectra set.…”

Photoemission study of (PbEuGd)Te layers under Gd or Te atoms treatment

“…A weak broad structure with maximum at 7.5 eV can be attributed to the Eu 3+ 4f multiplet. The value of the resonance energy Eu 4d → 4f transition for 2+ ions of europium in our samples is at about 141 eV and antiresonance energy at 132 eV while for 3+ ions it is at about 145 eV and 139 eV relatively [8][9][10][11]. The spectra well correspond to DOS calculation of EuTe by augmented-plane-wave (APW) method [12,13], in which Eu 2+ 4f states were found at top of the occupied electronic states and they are located at the edge (Γ 15 ) of the valence band.…”