We consider the square lattice Heisenberg antiferromagnet with plaquette ring exchange and a finite interlayer coupling leading to a consistent description of the spin-wave excitation spectrum in La2CuO4. The values of the in-plane exchange parameters, including ring-exchange J_{\Box}, are obtained consistently by an accurate fit to the experimentally observed in-plane spin-wave dispersion, while the out-of-plane exchange interaction is found from the temperature dependence of the sublattice magnetization at low temperatures. The fitted exchange interactions J=151.9 meV and J_{\Box}=0.24 J give values for the spin stiffness and the Neel temperature in excellent agreement with the experimental data.
@article{arxiv.cond-mat/0111533,
title = {Spin Excitations in La2CuO4: Consistent Description by Inclusion of Ring-Exchange},
author = {A. A. Katanin and A. P. Kampf},
journal= {arXiv preprint arXiv:cond-mat/0111533},
year = {2009}
}