Abstract
A second-order Green function theory is developed for a two-sublattice antiferromagnet using the random phase decoupling approximations (RPA). Calculations are carried out for a simple cubic as well as for a body-centred cubic lattice and all values of spin and the transition temperature, where the paramagnetic staggered susceptibility chi st diverges, is obtained. Results for the paramagnetic susceptibility and other thermodynamic quantities of interest are also derived and are found to be identical with those of Fujii (1974) in the high-temperature limit. A series for chi st is also obtained and is found to be in satisfactory agreement with the results of Rushbrooke and Wood (1963).