Regensburg 2013 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 40: Poster Session Correlated Electrons

TT 40.42: Poster

Mittwoch, 13. März 2013, 15:00–19:00, Poster D

Pulsed-field experiments on the quasi-2d antiferromagnet Cs₂CuBr₄ — •Lars Postulka, Bernd Wolf, Pham Thanh Cong, Natalia van Well, Franz Ritter, Wolf Assmus, and Michael Lang — PhysikalischesInstitut, Goethe-Universität Frankfurt (M), SFB/TR 49, D-60438Frankfurt (M), Germany

We present pulsed-field measurements up to 50 T of the longitudinal elastic constant c₁₁ for 1.5 K < T < 4.2 K on single crystalline samples of Cs₂CuBr₄, aiming at identifying the signatures of the proposed spin liquid in the material’s elastic properties. A large softening, caused by the coupling of the quasi-2d spin fluctuations to the phonon system, is observed for magnetic fields smaller than the critical field B_c 31 T (B//a), an effect which is more pronounced for lower temperatures. As expected, in the fully-polarized state the c₁₁ mode is field independent for all temperatures. We compare the magnetoelastic properties of Cs₂CuBr₄ with those of Cs₂CuCl₄ which is less frustrated and according to neutron scattering data can be characterized as a spin liquid. In the latter material the quantum-critical point is located at B_c = 8.5 T (B//a). In addition, we present a set-up for high precision-magnetization measurements in pulsed fields. The results of the experiments on Cs₂CuBr₄ will be discussed in connection with the ultrasonic data.