Berlin 2008 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 32: Correlated Electrons: Poster Session
TT 32.59: Poster
Donnerstag, 28. Februar 2008, 14:00–18:00, Poster B
Magnetic ordering in organic transition-metal compounds — •L. Huang1, R. Beyer1, T. Papageorgiou1, O. Ignatchik1, T. Herrmannsdörfer1, J. Wosnitza1, S. Gemming2, J. Manson3, and J. Schlueter4 — 1Hochfeld-Magnetlabor Dresden (HLD), Forschungszentrum Dresden-Rossendorf (FZD), D-01314 Dresden, Germany — 2Institut für Ionenstrahlphysik und Materialforschung (FZD) — 3Department of Chemistry and Biochemistry, Eastern Washington Univ., Cheney, USA — 4Materials Science Division, Argonne National Laboratory, Argonne, USA
The magnetic properties of metalorganic compounds attract much attention as their structural and electronic exchange dimensionality can vary between one and three. Here, we present data of representatives which exhibit magnetic ordering and have been recently investigated by means of magnetometry and calorimetry. In the quasi-cubic compound [Cu(HF2)(pyz)2]BF4, we have observed an antiferromagnetic (AF) ordered phase occurring at TN = 1.6 K and a rich magnetic phase diagram up to 14 T as well. Above TN, the specific heat of that compound is in reasonable agreement with the predictions of the model for a s =1/2 2D square lattice quantum Heisenberg AF describing the in-plane exchange via the Cu−F−H−F−Cu bonds. In the quasi-1D compound Mn(glycine)(H2O)2Cl2 which is structurally arranged in helical chains, we have observed an unexpected 3D AF ordering at TN = 0.84 K, both in the results of the heat capacity and ac susceptibility. Probably, the 3D exchange is mediated by hydrogen bonds between the chains in addition to Mn−O−Mn bonds along the chains.