Berlin 2012 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 38: Correlated Electrons: Spin Systems and Itinerant Magnets 1
TT 38.6: Vortrag
Donnerstag, 29. März 2012, 10:45–11:00, H 3010
Pulse field ultrasonic experiments in the quasi-2d antiferromagnet Cs2CuBr4 — •Bernd Wolf, Pham Thanh Cong, Natalia Krüger, Franz Ritter, Wolf Assmus, and Michael Lang — Physikalisches Institut Goethe-Universität, SFB/TR 49; Frankfurt
The insulator Cs2CuBr4 is a frustrated quasi-twodimensional triangular lattice (bc plane) spin-1/2 Heisenberg antiferromagnet (HAFM) with a weak interlayer coupling. The long-range antiferromagnetic order (TN = 1.4 K at B = 0) can be suppressed to TN = 0 in a magnetic field Bc 31 T (B//a). For temperatures T > TN the magnetic properties of the material are dominated by quasi-2d spin fluctuations, which are also present in the ordered magnetic state. Here we present pulsed field measurements up to 50 T of the longitudinal elastic constants c11 for 1.2 K < T < 4.2 K. A large softening, caused by the coupling of the quasi-2d spin fluctuations, is observed for magnetic fields smaller than Bc, which is more pronounced for lower temperatures. As expected, in the fully polarized state, the c11 mode is field independent for all temperatures. In addition, we compare the magnetoelastic properties of Cs2CuBr4 with those of the isostructural quasi-2D HAFM Cs2CuCl4.