Dresden 2014 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 23: Low-Dimensional Systems: Other Materials
TT 23.6: Talk
Monday, March 31, 2014, 18:00–18:15, BEY 81
Susceptibility measurements on a weakly coupled spin-dimer system consisting of nitronyl-nitroxid stable biradicals — •L. Postulka1, B. Wolf1, U. Tutsch1, P.T. Cong1, M. Baumgarten2, Y. Borozdina2, D. Strassel3, S. Eggert3, and M. Lang1 — 1Physics Institute, Uni Frankfurt SFB/TR 49, D-60438 Frankfurt, Germany — 2MPI for Polymer Research SFB/TR 49, D-55128 Mainz, Germany — 3Physics Department and Research Center OPTIMA SFB/TR 49, Uni Kaiserslautern, D-67663 Kaiserslautern, Germany
We present low-temperature susceptibility data on a spin S=1/2 dimer system consisting of nitronyl-nitroxid radicals which are bridged via tolan molecules. The material, exhibiting a double-layer structure, can be regarded as a quasi- 2D system. From SQUID magnetisation measurements on high-quality single crystals, an intra-dimer coupling constant of Jintra/kB≈9.6 K can be determined. In addition, the data reveal indications for an inter-dimer coupling of the order of 1 K. In order to look for magnetic field-induced ordering phenomena, AC-susceptibility measurements were performed down to temperatures as low as T=34 mK and magnetic fields up to B=10.5 T. For temperatures below T=250 mK, a double-peak structure was observed at fields between 8 T and 9.5 T consistent with the expectation based on the above-mentioned coupling constants. Furthermore, in the same temperature range another anomaly around B=4.5 T appears. For a detailed understanding especially with regard to the dimensionality of the interactions and the implications for the type of order that is realized here, Quantum Monte Carlo simulations are underway.