Berlin 2015 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 16: Bio- and Molecular magnetism

MA 16.1: Vortrag

Dienstag, 17. März 2015, 09:30–09:45, EB 202

Ferromagnetic Cluster Spin Wave Excitation in the High Spin Molecules Mn₁₈Sr and Mn₁₉ — •Siyavash Nekuruh¹, M. Klingele¹, J. Nehrkorn¹, K. Prsa¹, B. Burger², A.M. Ako², C.E. Anson², Y. Lan², A.K. Powell², and O. Waldmann¹ — ¹Physikalisches Institut, Universität Freiburg, Germany — ²Institut für Anorganische Chemie, Karlsruhe Institut für Technologie (KIT)

The ferromagnetically coupled molecule Mn₁₉ has attracted considerable interest in the past because of its huge high-spin ground state S = 83/2. From the chemistry point of view determining the exchange coupling constants and their comparison to e.g. ab initio result is of interest, while physically it is highly interesting to understand the spin-wave excitations in such a molecule. The huge Hilbert space and intricate topology of Mn₁₉ complicate the analysis of experimental data enormously, and hence the simpler molecules Mn₁₀ and Mn₁₈Sr, which can be regarded as model compounds for Mn₁₉, were studied.

We here present a detailed study of the magnetic excitations in Mn₁₈Sr and Mn₁₉ by INS. For the determination of the exchange constants of Mn₁₈Sr we used the positions of two cold peaks in the measured INS spectra and the magnetic susceptibility simultaneously for fitting. In Mn₁₉ one excitation is observed at low energies, which is not present in Mn₁₀ and Mn₁₈Sr and shows an uncommon temperature dependence. As a result Mn₁₉ cannot be treated by a non-interacting spin-wave picture, but requires an inherent many-body description.