Regensburg 2010 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 27: CE: Poster Session
TT 27.71: Poster
Mittwoch, 24. März 2010, 14:00–18:00, Poster D1
Field-induced effects near the mysterious low-temperature phase transition in the proposed spin-liquid system κ-(BEDT-TTF)2Cu2(CN)3 — •Rudra Sekhar Manna1, Mariano de Souza1, Andreas Brühl1, 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
The charge-transfer salt κ-(BEDT-TTF)2Cu2(CN)3, a Mott insulator with a 2D triangular lattice structure, is considered as a likely candidate for a quantum-spin liquid. We have studied this material by measuring the uniaxial expansion coefficients αi, the specific heat and magnetic susceptibility. The main observations are: (i) a pronounced in-plane (bc) anisotropy in αi, implying significant T-dependent lattice distortions, and (ii) a pronounced phase-transition anomaly at 6 K. By employing a Grüneisen-scaling Ansatz, we have been able to separate the corresponding contribution to the specific heat. The entropy release suggests that the spin degrees of freedom alone cannot account for the phase transition [1]. While the 6 K transition is insensitive to the application of a magnetic field up to 10 T, the highest field accessible, distinct field dependencies have been found which set in at somewhat higher temperatures for magnetic fields along the b-axis of one particular high-quality crystal. Based on measurements as a function of temperature at constant field and isothermal field sweeps, an anomaly diagram was able to be constructed.
[1] R. S. Manna et al., arXiv:0909.0718 (2009).