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TT: Fachverband Tiefe Temperaturen
TT 33: Low-Dimensional Systems: Other Materials
TT 33.2: Vortrag
Dienstag, 17. März 2015, 09:45–10:00, H 3010
Thermodynamic investigations of the quasi-2d triangular Heisenberg antiferromagnet Cs2CuCl2Br2 — •Ulrich Tutsch, Lars Postulka, Bernd Wolf, Michael Lang, Natalija van Well, Franz Ritter, Cornelius Krellner, and Wolf Assmus — Physikalisches Institut, Goethe-University Frankfurt (M), SFB/TR 49
0mm The system Cs2CuCl4−xBrx (0 ≤ x ≤ 4) is a quasi-two-dimensional Heisenberg antiferromagnet with a triangular in-plane arrangement of the spin-spin couplings. The ratio J′/J of the corresponding coupling constants determines the degree of frustration in the system and has been found to be 0.34 (x = 0) and 0.74 (x = 4) [1] for the border compounds. One may ask whether for some intermediate Br concentration an even higher degree of frustration can be reached. Indeed, some indications have been reported by Ono et al. [1]. Here, we present specific heat C and susceptibility χ measurements below 1 K in magnetic fields B up to 13.5 T for the intermediate compound Cs2CuCl2Br2, which, due to site-selective substitution, shows a well-ordered halide sublattice. Indications for an antiferromagnetic transition are observed around 90 mK for B = 0. A small field of B = 0.14 T is sufficient to fully suppress this anomaly. Taking into account the high saturation field of about 20 T, extrapolated from χ(T = const, B) scans at low temperatures, this small ordered region in the B-T plane clearly indicates a high degree of frustration in Cs2CuCl2Br2.
[1] T. Ono et al., J. Phys. Soc. Jpn. 74 (2005) Suppl. pp. 135-144.