Regensburg 2007 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 20: Correlated Electrons - Poster Session
TT 20.43: Poster
Mittwoch, 28. März 2007, 14:00–17:45, Poster A
Magnetic and electrical properties of EuC2 — •Oliver Heyer1, Derk Wandner2, Nils Hollmann1, Uwe Ruschewitz2, John Mydosh1, Axel Freimuth1, and Thomas Lorenz1 — 1II. Physikalisches Institut, Universität zu Köln, D-50937 Köln — 2Institut für Anorganische Chemie, Universität zu Köln, D-50939 Köln
We present measurements of the magnetization M, the specific heat cp and the resistance ρ of EuC2.This compound is interesting because Eu exists in the oxidation states +2 as well as +3. Thus EuC2 may be located between the pure ionic carbides of the divalent alkaline earth (CaC2, SrC2) and the metallic carbides of the trivalent lanthanides (LaC2, CeC2). Possibly, one may even change the valency under pressure or temperature variation. The magnetization and the specific heat data indicate a ferromagnetic ordering at Tc ∼ 12 K. According to a very small hysteresis EuC2 may be classified as a soft ferromagnet. Above Tc the resistance shows a semiconducting behaviour. With the onset of the magnetic order the resistance decreases over 4 orders of magnitude indicating a metal-insulator transition (MIT). Moreover, an applied magnetic field shifts the MIT temperature to higher values, resulting in a colossal magnetoresistance with changes in the resistivity up to 6 orders of magnitude. This behaviour strongly resembles the colossal magnetoresistance of the better-known system of Eu-rich EuO.