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arXiv · 1001.3755

Quantized antiferromagnetic spin waves in the molecular Heisenberg ring CsFe$_8$

J. Dreiser·O. Waldmann·C. Dobe·G. Carver·S. T. Ochsenbein·A. Sieber·H. U. Güdel·J. van Duijn·J. Taylor·A. Podlesnyak
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Abstract

We report on inelastic neutron scattering (INS) measurements on the molecular spin ring CsFe$_8$, in which eight spin-5/2 Fe(III) ions are coupled by nearest-neighbor antiferromagnetic Heisenberg interaction. We have recorded INS data on a non-deuterated powder sample up to high energies at the time-of-flight spectrometers FOCUS at PSI and MARI at ISIS, which clearly show the excitation of spin waves in the ring. Due to the small number of spin sites, the spin-wave dispersion relation is not continuous but quantized. Furthermore, the system exhibits a gap between the ground state and the first excited state. We have modeled our data using exact diagonalization of a Heisenberg-exchange Hamiltonian together with a small single-ion anisotropy term. Due to the molecule's symmetry, only two parameters $J$ and $D$ are needed to obtain excellent agreement with the data. The results can be well described within the framework of the rotational-band model as well as antiferromagnetic spin-wave theories.

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J. Dreiser, O. Waldmann, C. Dobe, G. Carver, S. T. Ochsenbein, A. Sieber, H. U. Güdel, J. van Duijn, J. Taylor, A. Podlesnyak. 2010-01-21. Quantized antiferromagnetic spin waves in the molecular Heisenberg ring CsFe$_8$. https://doi.org/10.1103/physrevb.81.024408

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