Dresden 2009 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 29: Correlated Electrons: Low-dimensional Systems - Materials 2

TT 29.5: Talk

Wednesday, March 25, 2009, 15:00–15:15, HSZ 301

Quantized Spin Waves in a Ferromagnetic Supertetrahedron: INS studies on Mn₁₀ — •S. Stuiber¹, O. Waldmann¹, Y. H. Lan², N. Ghenadie², A. K. Powell², and T. Unruh³ — ¹Physikalisches Institut, Universität Freiburg, D-79104 Freiburg, Germany — ²Institut für Anorganische Chemie, Universität Karlsruhe, D-76128 Karlsruhe, Germany — ³Technische Universität München, Forschungsneutronenquelle FRM-II, D-85747 Garching, Germany

Similar to extended systems also in a ferromagnetic cluster a spin-wave approach can be used to describe the low-lying magnetic excitations. In a cluster, however, it leads to quantized spin waves with discrete energies. In this work, we report inelastic neutron scattering (INS) experiments on a Mn₁₀ cluster, performed at the direct time-of-flight spectrometer TOFTOF (FRM-II). This molecule is comprised of an octahedron of Mn³⁺ ions enclosed by a tetrahedron of Mn²⁺ ions, forming a supertetrahedron. Ferromagnetic couplings between the Mn ions lead to a ground state with total spin S = 22. The spin waves then correspond to the states in the S = 21 sector. INS is the experiment of choice to investigate this kind of excitations, because of its favorable selection rules. In our experiment we observed these excitations and used spin-wave calculations as well as exact diagonalization studies to model the data and infer values for the exchange coupling constants.