Dresden 2009 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 29: Correlated Electrons: Low-dimensional Systems - Materials 2
TT 29.2: Vortrag
Mittwoch, 25. März 2009, 14:15–14:30, HSZ 301
Strongly dispersive magnetic excitations in Li2CuO2 — •W.E.A. Lorenz1, S.-L. Drechsler1, R. Kuzian3, W. D. Stein2, N. Wizent1, A. Hiess4, W. Schmidt5, R. Klingeler1, M. Loewenhaupt2, and B. Büchner1 — 1Leibniz Institute for Solid State and Materials Research (IFW) Dresden, Germany — 2Institut für Festkörperphysik, TU Dresden, Germany — 3Institute for Problems of Materials Science Krzhizhanovskogo 3, 03180 Kiev, Ukraine — 4Institut Laue Langevin, F-38042 Grenoble Cedex 9, France — 5Jülich Centre for Neutron Science JCNS, Jülich, Germany
We report on recent inelastic neutron scattering experiments on Li2CuO2 which is considered to be the prototypical ferromagnetic S=1/2 spin chain compound. Although Li2CuO2 has been subject to many experimental and theoretical studies, its magnetic dimensionality is still discussed controversially. This open question is resolved by our spectroscopic study providing a set of magnetic exchange parameters. We find that the magnon excitation is strongly dispersive only for moment transfer along the chains. Analysis of our data by means of linear spin wave theory provides unequivocal evidence that the compound is indeed a quasi-one-dimensional magnet. To be more specific, we find that the ferromagnetic nearest neighbor intra-chain coupling is the dominant magnetic interaction, but highly frustrated by competing antiferromagnetic next-nearest neighbor couplings. In comparison, the inter-chain exchange is relatively weak. Some of the magnetic properties of the material remain puzzling and will have to be discussed with respect to highly frustrated magnetism.