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MA: Fachverband Magnetismus

MA 4: Bio- und molekularer Magnetismus

MA 4.6: Talk

Monday, March 7, 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. Waldmann¹ — ¹Physikalisches 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.