Coordination-Induced Structure Of The Mg 2p Core Level In I-Znmgr Quasicrystals

We present a detailed analysis of Mg 2p photoemission (PE) spectra in icosahedral ZnMgR (R=Y, Ho, Er) quasicrystals and in the crystalline Zn(2)Mg Laves phase. Synchrotron-radiation PE measurements were performed on in situ cleaved single-grain samples at 10(-10) mbar pressure and low, 90-150 K, temperature. The analysis of Mg 2p PE spectra in Zn(2)Mg reveals a surface shift of the core level of -0.12 eV. The Mg 2p PE spectra in i-ZnMgR quasicrystals are essentially broadened as compared to spectra in Zn(2)Mg Laves phase. The effect is due to the coordination-induced structure of the Mg 2p levels. Different local surroundings of Mg atoms in quasicrystals induce both different shifts of the Mg 2p level and splittings of its spin-orbit components. The local coordination potential at different Mg sites in the quasicrystalline lattice is calculated on the basis of the face-centered icosahedral ZnMgY atomic structure data, recently determined from the pair distribution function analysis. The coordination shifts calculated are spread within an interval of about 0.3 eV, while the splittings of the 2p(3/2) component are of the order of 1-10 meV. The simulated theoretical Mg 2p PE spectra of fci-ZnMgR quasicrystals perfectly fit the experimental data.