Berlin 2015 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 33: Low-Dimensional Systems: Other Materials
TT 33.3: Vortrag
Dienstag, 17. März 2015, 10:00–10:15, H 3010
Weakly coupled spin-dimer systems based on stable organic biradicals — •Bernd Wolf1, Lars Postulka1, Ulrich Tutsch1, Martin Baumgarten2, Yulia Borozdina2 und Michael Lang1 — 1Physics Institute, Goethe-University Frankfurt (M), SFB/TR 49, D-60438 Frankfurt (M), Germany — 2Max-Planck-Institute for Polymer Research, SFB/TR 49, D-55128 Mainz, Germany
We present low-temperature susceptibility data of newly synthesized S = 1/2 spin-dimer systems consisting of stable organic biradicals, formed by bridging nitronyl-nitroxides (NN) and imono-nitroxides (IN) via tolane molecules. The choice of this bridging molecule ensures a moderately strong intra-dimer coupling constant Jintra/kB around 9.0 K (NN) and 4.3 K (IN). In addition, a weak coupling between the spin dimers of the order of 1 K can be inferred from high-temperature susceptibility data. The crystal structure suggests a 2D arrangement of the dimer units. To determine potential field-induced ordered phases, highest-resolution AC-susceptibility measurements have been performed down to a temperature of T = 27 mK and magnetic fields up to B = 10.5 T. We observed for both materials double-peak structures in the susceptibility below the saturation field. For a detailed understanding, especially with regard to the dimensionality of the magnetic interactions and the nature of the field-induced magnetic order, we compare the experimental results with measurements on metal-organic coupled dimer compound C36H48Cu2F6N8O12S2, which shows clear signatures of 2D physics [1].
[1] Tutsch et al., Nat. Commun. 5, 5169 (2014).