Regensburg 2007 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 20: Poster session

MM 20.42: Poster

Tuesday, March 27, 2007, 14:45–18:00, Poster C

Raman study of the semiconductor to metal phase transition in Fe_1−xCo_xSi (0 ≤ x ≤ 1) — •Dirk Menzel¹, Ana Maria Racu¹, Thorsten Donig¹, Klaus Doll², and Joachim Schoenes¹ — ¹Institut für Physik der Kondensierten Materie, TU Braunschweig, Mendelssohnstr. 3, 38106 Braunschweig, Germany — ²Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, 70569 Stuttgart, Germany

A complete Raman spectroscopy study of Fe_1−xCo_xSi with x between 0 and 1 is presented. All the 9 Raman active modes predicted by the factor group analysis are observed and assigned to the A, E and T symmetry species. A density functional calculation of the phonons in FeSi and in CoSi is consistent with the experimentally obtained frequencies of the Raman modes. When Co substitutes Fe in FeSi the most striking effect is a strong shift of the A-type mode of the transition element to a lower frequency. This shift is attributed to the different electronic surroundings of the vibrating atoms as follows: the interaction between the Co atoms is screened by the free electrons in the metallic compound CoSi in contrast to the semiconducting FeSi, leading to a decrease of the Raman mode frequency.