Dresden 2009 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 6: Postersession Correlated Electrons: (General) Theory, Low-Dimensional Systems, Kondo Physics, Heavy Fermions, Quantum-Critical Phenomena
TT 6.27: Poster
Monday, March 23, 2009, 13:00–16:45, P1A
Coupled spin S = 1 /2 dimer-systems based on nitronyl-nitroxide biradicals — Cong T. Pham1, Katarina Removic-Langer1, •Bernd Wolf1, Yulia D. Borzdina2, Evgeny A. Mostovich2, Martin Baumgarten2, and Michael Lang1 — 1Physikalisches Institut, Universität Frankfurt, SFB/TR49, 60438 Frankfurt(M) — 2Max-Planck-Institut für Polymerforschung, SFB/TR49, 55128 Mainz
Due to the collective behaviour of their magnetic excitations, arrays of coupled S = 1/2 spin-dimers in magnetic fields are of general interest in solid state physics as they can be considered as a gas of interacting bosons. Depending on whether the repulsion or the hopping of magnetic excitations dominates, the magnons (triplons) may form superlattices or undergo Bose-Einstein condensation (BEC). The investigation of BEC under various conditions, especially the comparison between field- and pressure-induced condensation, as well as the influence of dimensionality is a subject of current interest. In this contribution we will present a new class of coupled spin-dimer systems based on purely organic building blocks. We will show magnetic susceptibility and magnetization data of various nitronyl-nitroxide biradicals from which we extract the influence of the bridging ligands on the intra-dimer coupling constant J. The target materials show moderate values of their intra-dimer exchange coupling and indications for significant inter-dimer couplings. In addition, due to the huge variety of possible bridging ligands and their chemical modification, the magnetic exchange in nitronyl-nitroxide biradicals can be fine tuned.