Münster 1999 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 6: Niederdimensionale Spinsysteme
TT 6.4: Hauptvortrag
Montag, 22. März 1999, 15:30–16:00, F2
NaV2O5 – the first quarter-filled ladder compound — •C. Gros — Institut für Physik, Universität Dortmund, 44221 Dortmund
The mixed-valence (V+4.5) transition metal compound NaV2O5 is identified, with the help of a new X-ray diffraction study and a subsequent LDA-analysis as a quarter-filled ladder compound. The low-energy properties can be modelled by a 1D Heisenberg model with the spin-1/2 moments formed by electrons in V-O(1)-V bonding orbitals. Below TSP=34 K a structural phase transition occurs with coexisting charge ordering 2V+4.5→ V+4+V+5 and formation of local spin-singlets. We argue that the available data for the temperature dependence of the magnetic exchange constant (from susceptibility measurements) and for the magnon dispersion (from neutron scattering) allow to identify the charge-ordering pattern.