Electronic structure of β−Al3Mg2 and Al13Fe4 complex metallic alloys

We report a comparative study of the bulk electronic structure of two Al-based complex metallic alloys (CMAs), $\ensuremath{\beta}\ensuremath{-}{\mathrm{Al}}_{3}{\mathrm{Mg}}_{2}$ and ${\mathrm{Al}}_{13}{\mathrm{Fe}}_{4}$ using hard x-ray photoemission spectroscopy (HAXPES) interpreted on the basis of density functional theory (DFT) calculations. An experimental confirmation of the role of the Hume-Rothery mechanism for the stability of the $\ensuremath{\beta}\ensuremath{-}{\mathrm{Al}}_{3}{\mathrm{Mg}}_{2}$ phase is established by identification of a shallow pseudogap near ${E}_{F}$ from HAXPES that is corroborated by DFT. An almost parabolic shape of the density of states (DOS), a large $n$(${E}_{F}$), and plasmon loss features that are similar to Al metal show its nearly free-electron-like nature. In the case of ${\mathrm{Al}}_{13}{\mathrm{Fe}}_{4}$ the total DOS exhibits a shallow pseudogap due to Al $s$ -- Fe $d$ hybridization, which results in the DOS at ${E}_{F}$ [$n$(${E}_{F}$)] being large due to Fe $d$ states. However, the Al $s$ states show a deep pseudogap and this is revealed in HAXPES because of the large photoemission cross section of the $s$ states at high photon energies. The overall shape of the valence band is in excellent agreement with DFT for both the CMAs. The larger width of the Al core-level main peak and the plasmon loss peaks as well as the suppression of the intensities of the latter with respect to $\ensuremath{\beta}\ensuremath{-}{\mathrm{Al}}_{3}{\mathrm{Mg}}_{2}$ further underline the importance of $sp\text{\ensuremath{-}}d$ hybridization in ${\mathrm{Al}}_{13}{\mathrm{Fe}}_{4}$.