Berlin 2012 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 40: Correlated Electrons: Low-dimensional Systems - Materials 3
TT 40.10: Talk
Thursday, March 29, 2012, 17:30–17:45, H 0104
(contribution withdrawn)Effect of bond disorder on weakly-coupled spin-1/2 antiferromagnetic Heisenberg chains — •Matthias Thede1,2, Fan Xiao3, Elvezio Morenzoni1, Christopher Landee3, and Andrey Zheludev2 — 1Laboratorium für Festkörperphysik, ETH Zürich, Switzerland — 2Paul Scherrer Institut, Villigen-PSI, Switzerland — 3Department of Physics and Carlson School of Chemistry, Clark University, USA.
We study the effect of chemical disorder on magnetic ordering in the quasi-one-dimensional antiferromagnets Cu(py)2(Cl1−xBrx)2. The two end compounds are S = 1/2 linear-chain systems with J = 2.3 meV and J = 4.5 meV, for x = 0 and x = 1, respectively. Weak inter-chain interactions lead to long range order at TN = 1.1 K and TN = 0.7 K, respectively. Partial substituting Br for Cl randomizes the bond strength in the spin chains. We probe magnetic and thermodynamic properties of Cu(py)2(Cl1−xBrx)2 with susceptibility, specific heat and MuSR measurements. For all samples, the temperature dependence of the magnetic susceptibility follows expectations for a S=1/2 Heisenberg chain. Specific heat data reveals more interesting behavior. While at the Cl end a very slow decrease of TN with x is observed, on the Br side, suppression of TN relative to x=1 is much more rapid. This disparity in the behavior samples is consistent with MuSR measurements. For the two end-compounds and Cu(py)2(Cl0.95Br0.05)2, there is a clear evidence of static magnetic behavior below TN. However, Cu(py)2(Cl0.94Br0.06)2 show totally different muon spectra, indicating a strong in homogeneity of the static magnetization.