Derivation of the generalized Non Linear Sigma Model in the presence of   the Dzyaloshinskii-Moriya interaction
  We derive the long-wavelength non-linear sigma model for a two-dimensional Heisenberg system in the presence of the Dzyaloshinskii-Moriya and pseudodipolar interactions. We show that the system is a non-conventional easy-axis antiferromagnet, displaying an anomalous coupling between the magnetic field and the staggered order parameter. Our results are in good agreement with recent experimental data for undoped La2CuO4 compounds. 
L. Benfatto, M. Silva Neto, V. Juricic, C. Morais Smith