Dresden 2006 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 25: Correlated Electrons - Poster Session
TT 25.116: Poster
Mittwoch, 29. März 2006, 14:30–18:30, P1
Thermodynamic and transport properties of doped La2CoO4 — •E Rose1, N Hollmann1, J Baier1, M Benomar1, K Berggold1, M Cwik1, M Kriener1, D Meier1, A Tanaka2, T Lorenz1, and A Freimuth1 — 1II.Physikalisches Institut, Universität zu Köln, Germany — 2Department of Materials Science, Hiroshima University, Japan
Cobaltates are of special interest due to the possibility of spin-state transitions. This has been studied in detail in the insulator LaCoO3. Strontium doping drives LaCoO3 to a metal and induces ferromagnetic order [1,2]. Much less is known about the layered cobaltates La2−xSrxCoO4. We prepared single crystals and present a study of magnetic susceptibility, thermal and electric conductivity as well as thermal expansion and thermopower for a strontium doping range of 0.3≤ x≤ 0.8. All samples are insulators in the measured temperature range. The magnetic susceptibility is strongly anisotropic and deviates from Curie-Weiss-behaviour. The susceptibility was analyzed via cluster calculation [3]. Thermal transport measurements in a temperature range from 5K to 300K present a small anisotropy. In fields up to 14 Tesla a weak field dependence is found which is related to the magnetic ordering, in particular for La1.5Sr0.5CoO4. Positive Seebeck coefficients observed at room temperature suggest p-type conduction. Furthermore we studied the effect of physical pressure due to calcium doping.
[1] Berggold et al., Phys. Rev. B 72, 155116 (2005)
[2] Kriener et al., Phys. Rev. B 69, 094417 (2004)
[3] Tanaka et al., J. Phys. Soc. Jpn. 63, 2788 (1994)
Supported by the DFG through SFB 608