Berlin 2008 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 32: Correlated Electrons: Poster Session
TT 32.60: Poster
Donnerstag, 28. Februar 2008, 14:00–18:00, Poster B
Magnetostriction and thermal expansion of the spin-ladder compound (C5H12N)2CuBr4 — Thomas Lorenz1, •Fabrizio Anfuso2, Markus Garst2, Achim Rosch2, Oliver Heyer1, Christian Rüegg3, and Karl Krämer4 — 1Institute of Physics II, University of Cologne, Germany — 2Institute of Theoretical Physics, University of Cologne, Germany — 3Centre for Nanotechnology and Dep. of Phys. and Astronomy, University College London, UK — 4Department of Chemistry and Biochemistry, University of Bern, Switzerland
We present high-resolution measurements of the thermal expansion and magnetostriction of piperidinium copper bromide (C5H12N)2CuBr4. The experimental data at low and intermediate temperatures are very well described by a two-leg spin-ladder Hamiltonian with rung and nearest neighbor leg couplings. The thermal expansion shows a complex behavior with various sign changes and approaches a "one-dimensional" 1/√T divergence at the critical fields. As a consequence of a two-coupling constants model, the magnetostriction and thermal expansion along arbitrary spatial directions are always representable as linear combination of two simple spin correlation functions. We compute these functions with numerical and analytical methods and we find remarkable quantitative agreement along the three crystallographic directions for all the temperatures measured (from 400mK up to 8K !).
Supported by the DFG by through SFB 608.