Dresden 2011 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 19: Transport

MM 19.1: Vortrag

Dienstag, 15. März 2011, 14:00–14:15, IFW D

Transport and magnetic properties of non-stochiometric FeSi — Monika Kotzian, Tommy Reimann, Dirk Schulze Grachtrup, Stefan Süllow, and •Dirk Menzel — Institut für Physik der Kondensierten Materie, Technische Universität Braunschweig, Mendelssohnstr. 3, 38106 Braunschweig, Germany

Although the narrow-gap semiconductor FeSi has a non-magnetic ground state, it shows a residual Curie-like susceptibility at low temperature. Whereas this Curie-tail was generally attributed to a surplus of Fe³⁺, magnetic measurements imply that the residual susceptibility of samples with a slight Fe deficit is larger compared to samples with Fe excess. The transport properties of off-stochiometric tri-arc Czochralski-grown FeSi crystals have been investigated. The temperature dependence of the conductivity suggests that Anderson-localized states which stem from structural disorder carry the residual magnetic moment. Magnetoresistance measurements, which give some indications for a weakly localized system, support this interpretation. In addition, within an impurity model they show that the number of such localized states in the off-stochiometric samples is larger for Fe deficit than for Fe excess. Annealing experiments reveal that the off-stochiometry has a larger influence on the magnetic and transport properties than the presence of crystalline imperfections.