Soft X-ray photoemission study of the Heusler-type Fe2VAl1−zGez alloys

The valence-band electronic structures of the Heusler-type alloys Fe2VAl1−zGez (z = 0-0.10) have been investigated with high-resolution soft X-ray photoemission spectroscopy. The overall photoelectron spectral feature of Fe2VAl1−zGez with the Ge content z up to 0.10 is not so much changed, except for the main 3d band in the region from the Fermi level EF to the binding energy EB ∼ 1 eV. For z = 0.05, the leading edge of the main band is shifted by ∼0.07 eV, but the shift is much smaller than expected within a rigid band model for a calculated band structure. For z = 0.10, a band at EB ∼ 0.5 eV becomes prominent and the intensity of the Fermi edge is increased. The change in the valence band spectrum near EF suggests the rigid-band-like shift of the 3d bands and the appearance of new 3d states in the pseudogap, which may qualitatively explain the z-dependence of the thermoelectric properties. As z increases, the V 2p spectra show a shift towards the high binding energy and the evolution of a shoulder structure on the low binding energy side of the main line. The shoulder structure is attributed to the charge transfer to the V site induced by the Ge substitution as well as the surface effect. The change in the valence-band electronic structure is discussed in terms of the interaction between the substituted Ge and its surrounding constituent atoms.