4f occupation and hybridization from M-shell excitations in Rare-Earth materials

Abstract

Abstract M-shell excitations in Rare-Earth (RE) materials were studied using synchrotron radiation and total electron yield detection in UHV. In mixed-valent compounds of the heavy RE's (Sm, Eu, Tm), the M4,5 spectra are identified as superpositions of quasi-atomic 3d94fn+1 multiplet structures, providing quantitative information on the mean valence v (4f occupation) of the RE ions, even in highly dilute systems. The method employed in deriving quantitative values for v is described in some detail. Effects of 4f/valence-band hybridization on the M4,5 spectra are investigated for Ce systems: the 3d94f2 multiplet structure seen in γ-like Ce compounds is found to collapse in α-like systems, where satellites at about 5 eV higher energies are additionally observed. The method is also applied to dilute Ce systems, such as Ce in a Pd matrix, which is found to be α-like. In addition, M3-edge spectra are presented for a series of Ce compounds, and their relation to L3-edge spectra is discussed.