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MM: Fachverband Metall- und Materialphysik
MM 12: Postersitzung I
MM 12.11: Poster
Montag, 14. März 2011, 17:30–19:00, P5
Frozen phonon calculations confirm electron-phonon coupling in Fe1−xCoxSi — •Wilfried Wunderlich1 and Dirk Menzel2 — 1Tokai University, Fac. Eng., Material Science Department, Kitakaname 4-1-1, 259-1292 Hiratsuka, Japan — 2TU Braunschweig, Inst. f. Physik d. Kondensierten Materie, Mendelssohnstr. 3, 38106 Braunschweig, Germany
Thermoelectric measurements of the Seebeck voltage were performed on Fe1−xCoxSi single crystals under large temperature gradient [1]. They show an increase of a positive Seebeck coefficient as a function of Co-concentration for x < 0.05 up to 0.2 mV/K and a decrease for 0.05 < x < 0.2, and again an increase until x < 0.5 and a decrease for x > 0.7. The first increase is related to the semiconductor-metal transition, while the second increase around x = 0.6 corresponds to a paramagnetic ordering state and is discussed as caused by magnon-phonon-coupling. For each phonon mode several q-vector variants were generated, and using these frozen phonons DFT-GGA calculations using VASP were performed. The difference in bond-length spectrum in the presence of phonons changed the electronic bandstructure remarkably. Instead of the 200 meV wide band-gap in the case without phonons, flattening of the electronic bands and broadening of the DOS is observed. From these investigations the electron-phonon coupling constant can be derived.
[1] W. Wunderlich et al., Mater. Res. Soc. Symp. Proc. (2009) Vol. 1128-U01-10 pp. 1-6.