Energy distribution of Co and Ni 3d states of decagonal quasicrystal Al₇₂Co₁₆Ni₁₂

Abstract

The density of the Co and Ni 3d states of a decagonal quasicrystal Al₇₂Co₁₆Ni₁₂ has been investigated by Co and Ni 2p–3d resonance photoemission spectroscopy (XPS) and soft X-ray emission spectroscopy (XES) with synchrotron radiation as an excitation source. The valence-band photoemission spectrum recorded at the high excitation photon energy shows a single 3d band at the binding energy of 2 eV, which is higher than that obtained at the low excitation photon energy. This implies that the bulk 3d electronic states are different from the surface ones. The present resonance XPS and XES spectra also show that the Ni 3d-derived band is located at slightly higher binding energy than the Co 3d-derived one, in contrast with results reported so far. Comparison with the electronic structure calculated for a cluster simulating the local columnar atomic arrangement of the decagonal quasicrystal suggests rather random occupation of the transition metal sites by Co and Ni atoms.

Acknowledgements

The XPS measurements were performed with the approval of the Japan Synchrotron Radiation Institute (Proposal Nos.2002B0108-NS1-np and 2004A0386-NSa-np) and with the approval of Institute of Materials Structure Science (Proposal No.04G198). We thank the staff of the synchrotron radiation facilities, SPring-8, HiSOR, and Photon Factory, for their kind support during these measurements.