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Berlin 2012 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 47: Correlated Electrons: Spin Systems and Itinerant Magnets 2

TT 47.2: Talk

Friday, March 30, 2012, 09:45–10:00, H 0104

The strength of frustration and quantum fluctuations in LiVCuO4 — •Satoshi Nishimoto1, Stefan-Ludwig Drechsler1, Roman Kuzian1,2, Johannes Richter3, Jiři Málek1,4, Miriam Schmitt5, Jeroen van den Brink1, and Helge Rosner51IFW Dresden — 2Institute for Problems of Materials Science, Kiev, Ukraine — 3Universität Magdeburg — 4Institute of Physics, ASCR, Prague, Czech Republic — 5MPI für Chemische Physik fester Stoffe

We present an empirical and microscopical analysis of the in-chain exchange constants of the edge-shared frustrated chain cuprate LiVCuO4. We argue that the ferromagnetic nearest neighbour coupling J1 clearly exceeds the antiferromagnetic (AFM) next-nearest neighbour coupling J2. The measured saturation field is significantly affected by a weak 3D AFM interchain coupling leaving room for a possible Bose-Einstein condensation for several T below. The obtained exchange parameters are in agreement with the results for a realistic five-band extended HUBBARD Cu 3d O 2p model, LSDA+U predictions as well as with inelastic neutron scattering and magnetization data. The single chain frustration rate α=J2/|J1|≈ 0.75, including all error bars, is definitely smaller than 1. This corresponds to strongly coupled interpenetrating AFM Heisenberg chains in contrast with opposite statements in the literature. A proper account of strong quantum fluctuations and frustration is necessary for a correct assignment of the exchange integrals, which cannot be achieved by a simple renormalization of J2 from the spin-wave theory.

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