High-resolution photoelectron spectroscopy of Heusler-type Fe₂VAl alloy

The electronic structure of Heusler-type Fe₂VAl has been studied by high-resolution photoelectron spectroscopy with the excitation photon energy hν ranging from 21.2 eV (the He I laboratory light source) to 904 eV (the soft X-ray synchrotron light source) for clean surfaces prepared by scraping or fracturing polycrystalline and single crystalline specimens. Photoelectron spectra recorded for the fractured surfaces show a 10 eV-wide valence band with fine structures and a clear decrease in the intensity towards the Fermi level E_F, while a high intensity at E_F and no fine structures are observed for the scraped surface. Comparison with the theoretical density of states (DOS) indicates that the vacuum ultraviolet photoelectron spectra emphasize the transition-metal 3d bands but the soft X-ray photoelectron spectra agree remarkably well with the DOS including the fine structures and the pseudogap at E_F. The present results suggest that the electronic structure of Fe₂VAl is highly sensitive to possible strain and defects induced by scraping. Bulk electronic structures of Fe₂VAl are discussed in relation to the reported fascinating transport properties.