Journal
EPL
Volume 88, Issue 3, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1209/0295-5075/88/37002
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Funding
- DFG [KL1824/2, DR269/3-1]
- Emmy-Noether-program
- program PICS [CNRS 4767, NASU 243]
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We present an inelastic neutron scattering investigation of Li2CuO2 detecting the long-sought quasi-1D magnetic excitations with a large dispersion along the CuO2-chains studied up to 25 meV. The total dispersion is governed by a surprisingly large ferromagnetic (FM) nearest-neighbor exchange integral J(1) = -228 K. An anomalous quartic dispersion near the zone center and a pronounced minimum near (0,0.11,0.5) r.l.u. (corresponding to a spiral excitation with a pitch angle of about 41 degrees) point to the vicinity of a 3D FM-spiral critical point. The leading exchange couplings are obtained applying standard linear spin-wave theory. The 2nd neighbor inter-chain interaction suppresses a spiral state and drives the FM in-chain ordering below the Neel temperature. The obtained exchange parameters are in agreement with the results for a realistic five-band extended Hubbard Cu 3d O 2p model and L(S) DA+ U predictions. Copyright (C) EPLA, 2009
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