Spectroscopic study of Ni-rich Al–Co–Ni quasicrystal

Abstract

The valence-band electronic structure of a decagonal Ni-rich Al–Co–Ni quasicrystal, Al₇₂Co₈Ni₂₀, was investigated using soft X-ray photoelectron spectroscopy. In particular, the energy distributions of the transition metal 3d bands were determined from the Co and Ni 2p–3d resonance photoemission and compared with those calculated by the discrete variational Xα method for a model cluster based on a proposed Ni-rich Al–Co–Ni approximant, as well as the 3d band observed in the Co-rich Al–Co–Ni quasicrystal, Al₇₂Co₁₆Ni₁₂. In the Ni-rich Al–Co–Ni, the transition metal 3d band exhibits a peak at a binding energy, E _B, of 2.3 eV, which is higher than that of the Co-rich Al–Co–Ni. The observed Ni 3d band has a single-peaked distribution around E _B ∼ 2.4 eV, in contrast to the calculated bimodal and wide-spread distribution for the proposed Ni-rich Al–Co–Ni model cluster, whereas the Co 3d band is located at E _B ∼ 1.7 eV, consistent with the model calculation.

Keywords:

• valence-band electronic structure
• soft X-ray photoelectron spectroscopy
• DV-Xα cluster calculation
• decagonal quasicrystal
• Al₇₂Co₈Ni₂₀

Acknowledgements

The soft X-ray photoelectron measurements were performed at the beamline BL27SU of SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (JASRI) (Proposal Nos. 2009A1672 and 2009B1729).