Berlin 2015 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 72: Low-Dimensional Systems: Poster Session
TT 72.14: Poster
Mittwoch, 18. März 2015, 15:00–18:00, Poster B
Field-induced ordered phases in coupled spin-dimer systems — •L. Postulka1, B. Wolf1, U. Tutsch1, M. Baumgarten2, Y. Borozdina2, D. Straßel3, S. Eggert3, and M. Lang1 — 1Physics Institute, Goethe-University, SFB/TR 49, D-60438 Frankfurt (M) — 2Max-Planck-Institute for Polymer Research, SFB/TR 49, D-55128 Mainz — 3Physics Department and Research Center OPTIMAS, University of Kaiserslautern, D-67663 Kaiserslautern
Materials built of antiferromagnetically-coupled S=1/2 dimers, allow to study finite-temperature critical phenomena under well-controlled conditions. Examples are the Bose-Einstein-condensation of magnons in 3D systems and Luttinger-liquid behaviour in 1D. In pure 2D materials one expects so-called topological order associated with the binding of vortices with opposite circulation as suggested by Berezinskii, Kosterlitz and Thouless. We present susceptibility data down to 27 mK of a newly synthesised S=1/2 spin dimer systems consisting of stable organic biradicals. The crystal structure suggests a 2D arrangement of the coupled dimers. We observe a field-induced ordered state characterized by a rounded double-peak structure. To obtain detailed information about the nature of the field-induced ordered phase we measured the temperature dependence of the susceptibility at the critical fields. These results are compared with quantum Monte Carlo simulations and measurements on a metal-organic compound, composed of layers of S=1/2 dimers, which lacks long-range 3D magnetic order down to at least 27 mK, but instead shows distinct 2D behaviour in its magnetic properties[1].
[1] Tutsch et al., Nat. Commun. 5, 5169 (2014)