Regensburg 2004 – wissenschaftliches Programm
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MA: Magnetismus
MA 21: Bio- und molekularer Magnetismus
MA 21.5: Vortrag
Donnerstag, 11. März 2004, 11:15–11:30, H22
Magnetic correlations in oxalate spin ladders — •C. Mennerich1, M. Bröckelmann1, J. Kreitlow1, A. Wolter1, S. Süllow1, F.J. Litterst1, R. Klingeler2, B. Büchner2, D.-J. Price3, and H.-H. Klauss1 — 1Institut für Metallphysik und Nukleare Festkörperphysik, TU Braunschweig — 2Leibniz-Institut für Festkörper- und Werkstoffforschung, Dresden — 3Department of Chemistry, Univ. of Southampton, United Kingdom
We present studies of the magnetic behaviour in the isostructural spin ladder materials Na2T2(C2O4)3(H2O)2 with T= Ni, Co, Fe, Mn (J. Chem. Soc., Dalton Trans. 2000, 3566 ). Here the oxalate (C2O4)2− molecule acts as the bridging element in the rungs and legs of the transition metal ladder. We performed magnetic susceptibility and high field magnetization as well as Moessbauer spectroscopy (Fe system only). The susceptibility of all systems shows a pronounced maximum between 10 and 25 K indicating an antiferromagnetic interaction. The data can be described using a dimer model representing two metal centers in the 2+ high spin state with a dominant magnetic interaction along the rungs of the ladder. An additional weak interaction along the legs is treated in mean field approximation. Moessbauer spectroscopy on the Fe compound revealed a temperature dependent electric field gradient (EFG) due to crystal field splitting and prove a Fe(II) S=2 configuration. No magnetic order is found down to 2K.