Electronic structure of beta-Al3Mg2 and Al13Fe4 complex metallic alloys

We report a comparative study of the bulk electronic structure of two Al-based complex metallic alloys (CMAs), beta-Al3Mg2 and Al13Fe4 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 beta-Al3Mg2 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 Al13Fe4 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 beta-Al3Mg2 further underline the importance of sp-d hybridization in Al13Fe4.