Binding energies and work-function changes inEuxLa1−xAl2compounds studied by x-ray photoelectron spectroscopy

Abstract

The intermetallic compound ${\mathrm{Eu}}_x{\mathrm{La}}_{1-x}{\mathrm{Al}}_2$ has been studied by x-ray photoelectron spectroscopy with A1 $K\alpha$ radiation at concentrations $x=0, 0.03, 0.1, \mathrm{and} 1$. The dependence of the Eu-$4f$ line shape on the partial density of states at the Fermi energy is discussed. The Eu-$4f$ excitation energy in the compounds was found to be ${\Delta }_{-}=1.0\mathrm{}\pm 0.1$ eV independent of the Eu concentration. This is 0.9 eV smaller than the value reported for metallic Eu. The energy shift is mainly due to Fermi-energy changes as confirmed by work-function measurements of the samples. The resultant shift is discussed in terms of charge transfer together with existing Mössbauer-isomer-shift data.