Dresden 2006 – scientific programme

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TT: Tiefe Temperaturen

TT 25: Correlated Electrons - Poster Session

TT 25.34: Poster

Wednesday, March 29, 2006, 14:30–18:30, P1

Competing magnetic interactions in 1D and 2D cuprates - an electronic structure study — •Ulrike Nitzsche¹, Stefan-Ludwig Drechsler¹, and Helge Rosner² — ¹IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany — ²MPI CPfS Dresden

In many copper oxygen networks, especially for Cu-O-Cu bond angles close to 90^∘, ferromagnetic interactions play an important role in addition to the well known superexchange J ∼ t²/U. We present a systematic study of the electronic structure and the exchange integrals for different types of 1D and 2D spin 1/2 cuprate systems: edge and corner shared single-chain (Li₂CuO₂, Sr₂CuO₃), double-chain (SrCuO₂), and planar (CaCuO₂, Sr₂CuO₂Cl₂) arrangements. Based on full potential LSDA and LSDA+U band structure calculations and subsequently derived tight-binding models we estimate sign and magnitude of the most relevant exchange integrals. We compare the results of total energy calculations with those of various tight-binding (TB) models from one-band and multi-band approaches. The ferromagnetic contributions can be estimated from the difference between the TB and the total energy results. We investigate the effect of the network configuration (edge shared vs. corner shared CuO₂ plaquettes) and of the dimensionality on the coupling strength.