Magnetic order and spin excitations in layered Heisenberg   antiferromagnets with compass-model anisotropies
  The spin-wave excitation spectrum, the magnetization, and the N\'{e}el temperature for the quasi-two-dimensional spin-1/2 antiferromagnetic Heisenberg model with compass-model interaction in the plane proposed for iridates are calculated in the random phase approximation. The spin-wave spectrum agrees well with data of Lanczos diagonalization. We find that the Neel temperature is enhanced by the compass-model interaction and is close to the experimental value for Ba2IrO4. 
A.A. Vladimirov, D. Ihle and N. M. Plakida
cond-mat.str-el