Berlin 2005 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 17: Symposium Quantum Magnetism in Molecule-based Materials
TT 17.6: Vortrag
Montag, 7. März 2005, 12:45–13:00, TU H104
Magnetic properties of a molecular based antiferromagnet on a honeycomb lattice — •Ivan Spremo and Peter Kopietz — Institut für Theoretische Physik, Universität Frankfurt, Robert-Mayer-Str. 8, 60054 Frankfurt am Main
Using a modified spin-wave approach and exact diagonalizations we have calculated the finite-temperature magnetization curve M ( H ) of a two-dimensional quantum Heisenberg antiferromagnet on a honeycomb-lattice in a uniform magnetic field H. Our theoretical curve for M ( H ) agrees reasonably well with recent experimental data obtained for a molecular based antiferromagnet with stoichiometric formula C22H18MnO8. We also discuss the nature of the spin-excitations of quantum antiferromagnets in a uniform magnetic field at zero temperature. We show that below three dimensions the coupling between transverse and longitudinal spin fluctuations leads to a breakdown of the quasi-particle concept for magnons.