Regensburg 2013 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 55: Correlated Electrons: Low-Dimensional Systems -Materials 2
TT 55.6: Vortrag
Donnerstag, 14. März 2013, 10:45–11:00, H21
A metal-organic spin-1/2 dimer system yielding a 2d field-induced collectively-coupled dimer phase — •U. Tutsch1, B. Wolf1, T. Kretz2, H.-W. Lerner2, M. Wagner2, S. Wessel3, T. Saha-Dasgupta4, H. Jeschke5, R. Valenti5, and M. Lang1 — 1Phys. Inst., Goethe-Universität, 60438 Frankfurt — 2Inst. f. Anorg. Chemie, Goethe-Universität, 60438 Frankfurt — 3Inst. f. Theoret. Festkörperphysik, RWTH Aachen, 52056 Aachen — 4S.N. Bose National Centre for Basic Sciences, Salt Lake City, Kolkata 700098, India — 5Inst. f. Theoret. Physik, Goethe-Universität, 60438 Frankfurt
Spin-dimer systems have proven to be very useful in studying magnetic field-induced phase transitions. Here, we present high-resolution susceptibility and specific heat measurements at very low temperatures down to 0.040 K on the metal-organic spin-1/2 dimer system C36H48Cu2F6N8O12S2. The intra-dimer coupling between the spins on the Cu sites is Jd/kB≈10 K, making field-induced ordering accessible for standard laboratory magnets. Ab initio calculations suggest an effective two-dimensional (2d) structure with inter-dimer couplings Ji of at least an order of magnitude smaller than Jd. This is confirmed by comparison of the experimental data with results form Quantum Monte Carlo simulations for 1d, 2d and strongly anisotropic 3d coupling schemes. We identify a region in the field vs. temperature phase diagram where the system exhibits typical 2dXY behaviour accompanied by the formation of vortices and antivortices in the effective spin configuration. The possibility of a magnetic Berezinskii-Kosterlitz-Thouless transition will be discussed.