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TT: Tiefe Temperaturen
TT 19: Correlated Electrons: Low-dimensional Materials
TT 19.7: Vortrag
Dienstag, 28. März 2006, 15:30–15:45, HSZ 301
Electronic structure and magnetic properties of the spin-1/2 system Bi2CuO4 — •Oleg Janson1,2 and Helge Rosner1 — 1MPI CPfS Dresden — 2SPbSU St. Petersburg, Russia
Bi2CuO4 crystallizes in the tetragonal system, with isolated CuO4 plaquettes arranged parallel to the xy plane and staggered in chains along the z axis. Initially, Bi2CuO4 was treated as 1D compound, but low temperature data, especially the magnetic moment of 0.93 µB, show that quantum fluctuations are strongly suppressed and exclude a 1D model. Neutron scattering data reveal FM-ordered chains along z, that are AFM ordered with respect to each other [1]. To elucidate the origin of the surprisingly FM-ordered chains, we performed DFT calculations to evaluate the relevant orbitals and couplings. Total energy calculations yield a magnetic groundstate coinciding with the experimental data. From a tight-binding fit of the LDA band structure we obtained the exchange integrals. The most important result is that the main coupling is between the chains and the in-chain interaction is relatively small. Thus, the FM arrangement of chains is due to strong AFM exchange of neighbouring plaquettes that belong to the different chains. Therefore, Bi2CuO4 has to be described as a compound with 3D coupling.
This investigation was supported by the DFG, Emmy Noether-program
[1] J. L. García-Muñoz, J. Rodríguez-Carvajal et al. J. Phys.: Condens. Matter, 2 (1990) 2205–2214