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TT: Fachverband Tiefe Temperaturen

TT 13: Correlated Electrons: Low-dimensional Systems - Materials 1

TT 13.13: Talk

Tuesday, February 26, 2008, 12:45–13:00, H 2053

Competing exchange interactions in the one-dimensional spin-1/2 system Li₂CuO₂ — •Ulrike Nitzsche¹, Stefan-Ludwig Drechsler¹, and Helge Rosner² — ¹IFW Dresden, P.O. Box 270116, D-01171 Dresden — ²MPI CPfS Dresden, Nöthnitzer Straße 40, D-01187 Dresden

The spin 1/2 chain-cuprate Li₂CuO₂ is the archetype for competing nearest-neighbor and next-nearest-neighbor exchange interaction J₁ and J₂ along the CuO₂ chains. The magnitude of J₁ and J₂, especially their ratio α is crucial for the understanding of the magnetic ground state and is controversially disputed since a decade. Here, we report a density functional based electronic structure study to evaluate the leading in-chain and inter-chain exchange constants. We combine an LDA+U total energy approach for different spin configurations with the results from a tight-binding fit mapped onto a Heisenberg model. Our results yield a ferromagnetic ground state with a ferromagnetic J₁ and an antiferromagnetic J₂ and an α value well inside the region of the ferromagnetically ordered phase. A brief comparison with results from literature is given.