Dresden 2003 – wissenschaftliches Programm

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MA: Magnetismus

MA 23: Bio-und molekularer Magnetismus

MA 23.3: Vortrag

Donnerstag, 27. März 2003, 10:45–11:00, HSZ/401

1H-NMR on the cyclic spincluster Fe6(tea)6 — •R. Leppin, E. Herrling, and B. Pilawa — Physikalisches Institut, Universität Karlsruhe (TH), Karlsruhe, Germany

The Fe6(tea)6-spincluster forms a ring of 6 antiferromagnetically coupled FeIII-ions. The electronical spindynamics can be observed by proton NMR. T1-rates have been measured for a single crystal and a powdersample between 4K and 300K. For the single crystal the external field was applied parallel and perpendicular to the molecular symmetry axis. The results are compared with 1H-NMR measurements on Na@Fe6(tea)6. For decreasing temperature, all samples show a linear decrease in the T1-rate down to a minimum at ∼80K. Then the rate increases up to a maximum at ∼30K. Below that temperature a sharp drop is observed, due to the energy gap between the groundstate S=0 and the first excited states of the electronic system. The comparison of different powdersamples shows a correlation between the T1-rate and the exchange coupling constants of the FeIII-ions. The observed T1-rates are higher than those reported in the literature due to the smaller average distance between the protons and the FeIII-ions in our systems.

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