Berlin 2005 – scientific programme
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MA: Magnetismus
MA 14: Molekularer Magnetismus
MA 14.10: Talk
Saturday, March 5, 2005, 16:00–16:15, TU H1012
Simulation of Frequency Domain Magnetic Resonance Spectra on Molecular Magnets — •Nadeschda Kirchner, Joris van Slageren, and Martin Dressel — 1. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart
The FDMRS-technique is an advanced method that allows direct determination of the Zero Field Splittings (ZFS) in magnetic molecules in absence of an external magnetic field. Here we report a FDMRS study on (PPh4)[Mn12O12 (O2CEt) 16(H2O)4], [Mn9O7(OAc) 11 (thme)(py) 3 (H2O) 2], [Ni(Himpy) 2NO3](NO3) and [Ni4 (MeOH) 4 (sae) 4] complexes, in powder form. The FDMRS-spectra of these molecules were simulated in the strong-exchange limit within the ground spin multiplet for all complexes mentioned above. The ZFS-parameters were fitted to the absorption line positions observed in the FDMRS-experiment; they correlate well with those obtained by INS measurements.
We are currently exploring the simulation of FDMRS spectra beyond the strong exchange/spin only approximation. On one hand we are interested in how the simulated magnetic resonance spectrum changes when considering the isotropic exchange interaction and magnetic anisotropy. On the other hand we are interested in orbitally degenerate systems. As an example the results obtained for the [Ni4 (MeOH) 4 (sae) 4] cluster will be shown. The comparison of the FDMRS-measurements with their simulation resulting from irreducible tensor operator calculations and the discussion of the origin of magnetic anisotropy in the cluster will be presented.