Dresden 2009 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 16: Correlated Electrons: Low-dimensional Systems - Materials 1
TT 16.3: Vortrag
Dienstag, 24. März 2009, 10:00–10:15, HSZ 304
Magnetic field-induced ordering in a metal-organic spin-1/2 dimer system – a candidate for a Kosterlitz-Thouless transition — •U. Tutsch1, B. Wolf1, M. Lang1, T. Kretz2, H.-W. Lerner2, M. Wagner2, S. Wessel3, T. Saha-Dasgupta4, H. Jeschke5, and R. Valenti5 — 1Phys. Inst., Goethe-Universität, SFB/TRR49, D-60438 Frankfurt (M), Germany — 2Inst. f. Anorg. Chemie, Goethe-Universität, SFB/TRR49, D-60438 Frankfurt (M), Germany — 3Inst. f. Theor. Phys. III, Universität Stuttgart, D-70550 Stuttgart, Germany — 4S.N. Bose National Centre for Basic Sciences, Salt Lake City, Kolkata 700098, India — 5Inst. f. Theor. Phys., Goethe-Universität, SFB/TRR49, D-60438 Frankfurt (M), Germany
We have investigated the spin-1/2 metal-organic dimer system C36H48Cu2F6N8O12S2 (TK91) by means of high-resolution susceptibility measurements at very low temperatures (0.04 K ≤ T ≤ 0.5 K) and magnetic fields up to B=7.5 T. The spins, located on the Cu2+ ions, are coupled into dimers by a hydroquinone-derived linker, giving rise to an intra-dimer exchange interaction of J1/kB≈10 K. As suggested by ab initio calculations, the inter-dimer couplings Ji have a quasi-two-dimensional (quasi-2d) character with a very weak inter-layer coupling. Quantum Monte Carlo simulations for 2d and various strongly anisotropic 3d coupling schemes are used to model our susceptiblity data yielding clear signatures of a B-induced ordering phenomenon. A very good agreement is obtained for the 2d scenario, making TK91 a good candidate for the very rare phenomenon of a magnetic Kosterlitz-Thouless transition.