Berlin 2008 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 32: Correlated Electrons: Poster Session

TT 32.31: Poster

Donnerstag, 28. Februar 2008, 14:00–18:00, Poster B

Preparation and Characterization of BaCoO₂ and Sr-doped EuCoO₃ — •Marco Reuther, Kerstin Dönecke, John Mydosh, Thomas Lorenz, and Martin Valldor — II. Physikalisches Institut, Universität zu Köln, Germany

We have prepared polycrystals of BaCoO₂ and (Eu,Sr)CoO₃. BaCoO₂ is an air sensitive material whose physical properties are hardly explored. The structure of BaCoO₂ is trigonal with Co²⁺ ions in tetrahedral coordination [1]. Our magnetization measurements suggest a canted antiferromagnetic order with T_N≈370 K.

EuCoO₃ is insulating with Co³⁺ ions in the nonmagnetic low spin state up to about 400K [2]. Already small amounts of Sr induce a ferromagnetic order with T_C≈160 K due to the presence of Co⁴⁺ ions. Because of Co³⁺ remains in the low spin state we can observe the pure magnetic moment of Co⁴⁺ by Sr-doping. The electrical resistivity decreases with Sr but remains insulating.

[1] U. Spitsbergen et al., Acta Cryst. 13, 197 (1960).

[2] J. Baier et al., PRB 71, 014443 (2005)