1202.1268 (S. K. Choi et al.)

Spin waves and revised crystal structure of honeycomb iridate Na2IrO3    [PDF]

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

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.

View original: http://arxiv.org/abs/1202.1268