Dresden 2009 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 33: Bio- Molecular Magnetism
MA 33.4: Vortrag
Donnerstag, 26. März 2009, 11:00–11:15, HSZ 103
Symmetry assisted approximate diagonalization of antiferromagnetic molecules — •Roman Schnalle1 and Jürgen Schnack2 — 1Universität Osnabrück, Fachbereich Physik, D-49069 Osnabrück — 2Universität Bielefeld, Fakultät für Physik, Postfach 100131, D-33501 Bielefeld
The spectrum of many interesting molecular antiferromagnets is theoretically often inaccessible due to the prohibitive size of the underlying Hilbert space. Experimentally the system of interest might very well be accessible for instance by neutron scattering, EPR, specific heat or magnetization measurements. The interpretation of the experimental data thus suffers from numerical restrictions.
In order to get insight into the low-temperature behaviour of large spin systems describing magnetic molecules - either bipartite or frustrated - we develop an approximate diagonalization. This theory rests on the observation that the low-lying spectrum of many finite size antiferromagnets can be rather successfully approximated by so-called rotational bands [1], which are the eigenstates of the rotational band Hamiltonian. We use an increasing number of these basis states (bands) for an approximate diagonalization of the full Heisenberg Hamiltonian [2]. Additionally point-group symmetries are used for a further reduction of the dimensionalities of the occuring matrices and a specific labelling of the eigenstates.
[1] J. Schnack, M. Luban, Phys. Rev. B 63, 014418 (2000).
[2] O. Waldmann, Phys. Rev. B 75, 012415 (2007).