Dresden 2003 – wissenschaftliches Programm

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MA: Magnetismus

MA 23: Bio-und molekularer Magnetismus

MA 23.6: Vortrag

Donnerstag, 27. März 2003, 11:30–11:45, HSZ/401

Structural and magnetic investigations on a new molecule-based quantum magnet — •Volodymyr Pashchenko¹, Michael Lang¹, Bernd Wolf¹, Bernhard Brendel¹, Norbert Auner², Olga Shchegolikhina³, and Yulia Molodtsova³ — ¹Physikalisches Institut, Johann Wolfgang Goethe Universitat, Postfach 111932, 60054 Frankfurt am Main, Germany — ²Institut fur Anorganische Chemie, Jogann Wolfgang Goethe Universitat, Marie-Curie Str. 11, 60439, Frankfurt am Main, Germany — ³A.N.Nesmeyanov Institute of Organoelement Compounds (INEOS), 28 Vavilov Str., 117813 Moscow, Russia

We report results on a new hexacopper (II) siloxanolate cluster compound [C₉₂H₁₀₂Cu₆N₈O₂₉Si₁₀] crystallizing in the triclinic space group P1 (No.2). The unit cell has two identical macromolecules, each containing N=6 interacting Cu²⁺ ions with spin S=1/2. The magnetic susceptibility shows two different Curie-Weiss-type behaviors: The high-temperature (HT) state (100K<T<300K) is characterized by an average AF interaction with θ_HT=47K and a Curie constant C_HT=5.25 cm³K/mol, which lead to an effective No-dq12-spinNo-dq magnetic model. The low-temperature (LT) susceptibility (2K<T<15K) is characterized by an average AF interaction with θ_LT=1.05K and C_LT=1.61 cm³K/mol, indicating an effective No-dq4-spinNo-dq model. The temperature of the phase transition between No-dqHTNo-dq and No-dqLTNo-dq states is about 35 K. The state below 35 K can be understood in the following way: while 4 out of the 6 spins on each macromolecule form a non-magnetic S=0 state, the remaining 2 spins are coupled ferromagnetically giving rise to an effective S=1 cluster state.