It is shown that the experiments of A.M. Toader, J. P. Goff, M. Roger, N. Shannon, J. R. Stewart, and M. Enderle, Phys. Rev. Lett. 94, 197202 (2005) do not provide definitive experimental evidence for ring exchange terms in the Hamiltonian of La2CuO4, even though such terms may be present.
Cite
@article{arxiv.cond-mat/0510811,
title = {Comment on ``Spin Correlations in the Paramagnetic Phase and Ring Exchange in LaCuO''},
author = {L. Raymond and G. Albinet and A. -M. S. Tremblay},
journal= {arXiv preprint arXiv:cond-mat/0510811},
year = {2009}
}