Electronic density of states and metastability of icosahedral Au–Al–Yb quasicrystal

• Published in: Journal of alloys and compounds 2014-02, Vol.586, p.343-348
• Main Authors: Jazbec, S., Vrtnik, S., Jagličić, Z., Kashimoto, S., Ivkov, J., Popčević, P., Smontara, A., Kim, Hae Jin, Kim, Jin Gyu, Dolinšek, J.
• Format: Article
• Language: English
• Subjects: Alloys; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Density of states; Electrical transport; Electron states; Electronic conduction in metals and alloys; Electronic properties; Electronic structure of disordered solids; Electronic transport in condensed matter; Electronics; Exact sciences and technology; Gold; Icosahedral phase; Metastability; Physics; Quasicrystals; Stabilization
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2013.10.073

•Electronic stabilization of the metastable Al–Au–Yb quasicrystal is investigated.•Electronic density of states (DOS) near Fermi level was determined from thermopower.•The DOS shows the shape of a narrow valley with a spike at the Fermi level.•The valley is too narrow to be associated with the pseudogap for structure stabilization. The recently discovered icosahedral quasicrystal (i-QC) in the ternary Au–Al–Yb system at the composition Au51Al34Yb15 is formed only in as-cast alloys and is metastable with decomposition to other crystalline phases upon annealing at 700°C. Measuring the electronic transport coefficients (electrical resistivity, thermoelectric power, Hall coefficient), magnetic susceptibility and specific heat, we addressed the question of metastability of the i-Au–Al–Yb quasicrystalline phase by reconstructing the shape of the electronic density of states (DOS) in the vicinity of Fermi level ɛF with the aim to find out whether there exists a pseudogap in the DOS that could contribute to electronic stabilization of the icosahedral phase. The results have revealed that the DOS in the vicinity of ɛF exhibits a pronounced valley on a 100meV energy scale with a sharp feature on a 10meV scale, both being centered almost exactly at ɛF. This pseudogap is apparently not wide enough to ensure sufficient electronic energy gain of the order of a few 10kJ/mol needed for the electronic stabilization of the icosahedral phase. A possible origin of metastability of the i-Au–Al–Yb quasicrystal and thermodynamic stability of its 1/1 cubic approximant of very similar composition is discussed. The sharp feature in the DOS at ɛF is proposed to originate from indirect interaction between localized Yb f-moments due to overlap of their polarization clouds in the presence of hybridization of the f and s states, which leads to a sharp resonance peak.