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arXiv · 0909.5687

Highly Dispersive Spin Excitations in the Chain Cuprate Li2CuO2

W. E. A. Lorenz·R. O. Kuzian·S. -L. Drechsler·W. -D. Stein·N. Wizent·G. Behr·J. Malek·U. Nitzsche·H. Rosner·A. Hiess·W. Schmidt·R. Klingeler·M. Loewenhaupt·B. Buechner
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Abstract

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 J1=-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 about 41 degree 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 Ne'el 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.

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W. E. A. Lorenz, R. O. Kuzian, S. -L. Drechsler, W. -D. Stein, N. Wizent, G. Behr, J. Malek, U. Nitzsche, H. Rosner, A. Hiess, W. Schmidt, R. Klingeler, M. Loewenhaupt, B. Buechner. 2009-09-30. Highly Dispersive Spin Excitations in the Chain Cuprate Li2CuO2. https://doi.org/10.1209/0295-5075/88/37002

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