Dresden 2014 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 80: Low-Dimensional Systems - Poster Session
TT 80.14: Poster
Mittwoch, 2. April 2014, 15:00–19:00, P2
Dilatometric investigations on the quasi-2D organic charge-transfer salt κ-(ET)2Cu[N(CN)2]I — •Carola Dietrich1, Rudra Sekhar Manna1, John A. Schlueter2, and Michael Lang1 — 1Physikalisches Institut, Goethe-Universität Frankfurt, SFB/TR 49, D-60438, Frankfurt (M), Germany — 2Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, USA
High-resolution thermal expansion measurements have been performed on the quasi-two-dimensional organic charge-transfer salt κ-(ET)2Cu[N(CN)2]I along the in-plane c-axis and the out-of-plane b-axis for temperatures 1.4 K ≤ T ≤ 200 K. In accordance with previous studies [1], we find a highly anomalous expansivity at high temperatures followed by a pronounced glass-like transition for both axes. The glass-like transition at ∼ 84 K is similar to that observed for the related κ-(ET)2X salts with X = Cu[N(CN)2]Br and Cu[N(CN)2]Cl [2], and can be assigned to a freezing of orientational degrees of freedom of the terminal ethylene groups. The expansivity along the c-axis shows a hump-like anomaly at around 20 K, where a pronounced minimum was also observed in thermopower measurements [3]. We attribute the thermal expansion anomaly, which remains unaffected upon applying magnetic fields B ≤ 8 T, to short-range magnetic correlations. Upon further cooling, a rather small anisotropic anomaly is observed at around 5 K of unknown origin.
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