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Regensburg 2016 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 4: Bio- und molekularer Magnetismus

MA 4.6: Vortrag

Montag, 7. März 2016, 11:00–11:15, H33

Ferromagnetic Multi-Magnon Excitations in the High-Spin Molecule Mn19 — •Siyavash Nekuruh1, K. Prsa1, J. Nehrkorn1, B. Burger2, A.M. Ako2, C.E. Anson2, Y. Lan2, A.K. Powell2, and O. Waldmann11Physikalisches Institut, Universität Freiburg, Germany — 2Institut für Anorganische Chemie, Karlsruhe Institut für Technologie (KIT)

The ferromagnetically coupled molecule Mn19 with its world record high-spin ground state S = 83/2 has attracted considerable interest in the past. From the chemistry point of view determining the exchange coupling constants and their comparison to e.g. DFT calculations is of interest, while in physics understanding the spin-wave excitations in such a molecule is in the focus.

We here present a detailed study of the magnetic excitations in Mn19 by inelastic neutron scattering (INS). The INS spectra in the simpler model systems Mn10 and Mn18Sr were previously successfully interpreted in terms of ferromagnetic cluster spin waves. However, in Mn19 an additional excitation at low energies is present, which was not observed in Mn10 and Mn18Sr. It shows an unusual behaviour for exchange-only clusters, but is reminiscent of a collective excitation. We find that Mn19 cannot be treated in a non-interacting spin-wave picture; an inherent many-body description is required. Mn19 is thus a unique example of a magnetic molecule showing both cluster-type and collective-type magnetic excitations.

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