Dresden 2014 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 23: Low-Dimensional Systems: Other Materials
TT 23.1: Vortrag
Montag, 31. März 2014, 16:45–17:00, BEY 81
Huge magneto-elastic coupling and negative Poisson ratio in low-dimensional spin systems — •Bernd Wolf, Pham Thanh Cong, Rudra Sekhar Manna, Ulrich Tutsch, and Michael Lang — Physikalisches Institut, J.W. Goethe-Universität, SFB/TR49, D-60438 Frankfurt (Main), Germany
Azurite Cu3(CO3)2(OH)2, a model system for the distorted diamond-chain, exhibits pronounced elastic anomalies in the temperature - and magnetic field dependence of the longitudinal elastic mode c22. These features are assigned to the relevant magnetic interactions in the material and their couplings to the lattice degrees of freedom. From a quantitative analysis of the magnetic contribution to c22, the magneto-elastic coupling G = ∂ J2/ ∂ єb is determined, with єb denoting the strain along the chain b-axis. We find an exceptionally large value highlighting an extraordinarily strong sensitivity of J2 against changes of the b-axis lattice parameter. These results are complemented by measurements of the hydrostatic pressure dependence of J2 by means of thermal expansion and magnetic susceptibility measurements performed both at ambient and finite hydrostatic pressure. We discuss the results in light of an anomalous negative Poisson effect at low temperatures. We compare the results with the magneto-elastic coupling constants determined for other low-D quantum spin systems, such as the antiferromagnetic S = 1/2 Heisenberg spin chain based on a Cu-coordination polymer [1], the dimerized spin chain and SrCu2(BO3)2 as a coupled quasi-2D system [2].
B. Wolf, et al., Phys. Rev. B 69, 092403 (2004)
S. Zherlitsyn, et al., Phys. Rev. B 62, R6097 (2000)