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TT: Tiefe Temperaturen

TT 32: Correlated Electrons - Low-dimensional Materials II

TT 32.2: Vortrag

Dienstag, 8. März 2005, 16:30–16:45, TU H2053

Evidence for "ferromagnetic" helimagnetism in compounds with frustrated edge-shared CuO₂ chains — •S.-L. Drechsler¹, J. Richter², J. Málek¹, A. Moskvin³, H. Rosner⁴, A. Gippius⁵, R.E. Kremer⁶, and M. Enderle⁷ — ¹IFW-Dresden — ²Universität Magdeburg — ³Ural State University Ekaterinburg, Russia — ⁴MPI f. CPfS, Dresden — ⁵State University, Moscow, Russia — ⁶MPI f. Festkörperforsch., Stuttgart — ⁷Inst. Laue-Langevin, Grenoble, France

We present a combined theoretical and experimental study of the electronic structure and helimagnetism in compounds with frustrated edge-shared CuO₂ chains: LiVCuO₄ and LiCu₂O₂ vs. the ferromagnetic (fm) inchain ordering in Li₂CuO₂. Based on full potential L(S)DA and LSDA+U band structure calculations, exact diagonalization studies of multi-band Hubbard and Heisenberg models, we estimate sign and magnitude of the most relevant exchange integrals J. Strongly competing fm nearest neighbor (nn) and anti-fm next nn J’s are found for the inchain direction. This frustration scenario well describes magnetic susceptibility, specific heat, spin entropy, inelastic neutron scattering, and NMR data. The influence of interchain couplings is briefly discussed.