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arXiv · 1202.1268

Spin waves and revised crystal structure of honeycomb iridate Na2IrO3

S. K. Choi·R. Coldea·A. N. Kolmogorov·T. Lancaster·I. I. Mazin·S. J. Blundell·P. G. Radaelli·Yogesh Singh·P. Gegenwart·K. R. Choi·S. -W. Cheong·P. J. Baker·C. Stock·J. Taylor
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Abstract

We report inelastic neutron scattering measurements on Na2IrO3, a candidate for the Kitaev spin model on the honeycomb lattice. We observe spin-wave excitations below 5 meV with a dispersion that can be accounted for by including substantial further-neighbor exchanges that stabilize zig-zag magnetic order. The onset of long-range magnetic order below 15.3 K is confirmed via the observation of oscillations in zero-field muon-spin rotation experiments. Combining single-crystal diffraction and density functional calculations we propose a revised crystal structure model with significant departures from the ideal 90 deg Ir-O-Ir bonds required for dominant Kitaev exchange.

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S. K. Choi, R. Coldea, A. N. Kolmogorov, T. Lancaster, I. I. Mazin, S. J. Blundell, P. G. Radaelli, Yogesh Singh, P. Gegenwart, K. R. Choi, S. -W. Cheong, P. J. Baker, C. Stock, J. Taylor. 2012-02-06. Spin waves and revised crystal structure of honeycomb iridate Na2IrO3. https://doi.org/10.1103/physrevlett.108.127204

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