Electronic structure of Al-Cr-Fe intermetallics
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Electronic structure of Al-Cr-Fe intermetallics
Esther Belin-Ferré§, Zoltan Dankhazi$, Marie-Françoise Fontaine§, Jean Thirion§, Marie-Cécile de Weerd# and Jean Marie Dubois# § Laboratoire de Chimie Physique Matière et Rayonnement (UMR 7614), 11 rue Pierre et Marie Curie, F-75231 Paris Cedex 05. $ Institute for Solid State Physics, Lorand Eötvös University Budapest, Pazmany P. setany 1/A, H-1117 Budapest. # Laboratoire de Science et Génie des Matériaux et de Métallurgie, Centre d'Ingénierie des Matériaux, Ecole des Mines de Nancy, F-54042 Nancy.
ABSTRACT We report here the results obtained for the valence band of four compounds from the Al-CrFe system, all being approximants of the decagonal quasicrystalline phase as probed by a combination of X-ray emission and X-ray photoemission spectroscopy techniques. Salient features are d-d and p-d hybridizations at the Fermi level and in its close vicinity as well as a repulsive interaction between the d states of the two transition elements. Within about 4 eV below the Fermi level Al states are suggested to be of more localized-like character in the Al-CrFe samples than in Al-Cu-Fe ones.
INTRODUCTION In recent years, research on quasicrystalline systems has given impetus to the study of related complex intermetallics [1, 2]. Their physical properties are a matter of investigation and interest is also focused onto their atomic and electronic structures. Whereas the electronic structure of Al-Cu-Fe and Al-Co-Ni systems has been widely analyzed, to the best of our knowledge no such data is available for Al-Cr-Fe alloys. This has motivated the present experimental study of the electronic structure of various Al-Cr-Fe samples. The results presented here were obtained combining soft X-ray emission (SXES) and X-ray photoemission (XPS) spectroscopies that already proved useful for probing a number of Al based intermetallics. SXES scans separately the energy distribution of occupied electronic states of selected s, p, d, etc. character around each component of a sample [3]. In turn, XPS allows to measure electron binding energies and makes it possible to adjust the partial electronic distributions, as obtained by SXES, in the binding energy scale [4]. As a consequence, a picture of the valence band (VB) of the solid may be achieved, which makes it possible to point out the nature of electronic interactions in the sample.
EXPERIMENTAL DETAILS We have investigated four samples of nominal compositions: Al77.5Cr16.5Fe6, Al72.5Cr16.5Fe6B5, Al74.5Cr15Fe6B3Mo1.5 and Al70Cr10.5Fe10.5Cu9. The first sample is a decagonal
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compound with a faint quantity of an extra phase that cannot be a problem for our data because it is not detectable within the limits of our experimental accuracy. The same is true for the other samples that are essentially O1-orthorhombic approximants of the decagonal compound. The partial electronic distributions were probed using vacuum spectrometers fixed with a bent crystal or a grating with 600 groves/mm, as shown in Table 1. This table also give
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