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TT: Tiefe Temperaturen

TT 25: Correlated Electrons - Poster Session

TT 25.109: Poster

Mittwoch, 29. März 2006, 14:30–18:30, P1

Electron-Phonon Coupling in Fe_1−xCo_xSi as derived from Raman-Spectroscopy — •I. Jursic, T. Donig, A.-M. Racu, D. Menzel, and J. Schoenes — Institut für Physik der Kondensierten Materie, TU Braunschweig, Germany

FeSi is a paramagnetic semiconductor which is often viewed as Kondo insulator. Fe_1−xCo_xSi becomes a ferromagnetic metal with 0.05<x<0.8 whereas CoSi is a diamagnetic metal.

Raman measurements on Fe_1−xCo_xSi with different Co content were performed to investigate the effect of Co doping on the vibrational modes. The system crystallizes in the B20 structure which according to a factor group analysis yields 9 raman-active phonons that are all observed in the experiment.

Polarisation resolved measurements allow the identification of the A-mode. For increasing Co content a change in the intensities and distribution of the vibrational modes is observed. The E- and T-modes shift to higher energies contrary to the expectations. The A-mode shifts to lower energies more than expected. The shift of the modes begins with 10% Co content which is approximately at the insulator to metal transition.

Temperature resolved measurements show that the linewidth of one particular E mode strongly depends on the Co content. This is interpretated in terms of a strong electron-phonon coupling which leads to shorter decay times with increasing Co content and a closure of the energy-gap.