Softened spin-wave dispersion and sublattice magnetization at finite temperature for a three-dimensional anisotropic Heisenberg antiferromagnet

We study a three-dimensional anisotropic quantum antiferromagnetic Heisenberg model at finite temperature in which the interplanar coupling can be varied gradually, With the magnon interactions considered, we have calculated the spin-wave excitation and sublattice magnetization. We find that when the interplanar coupling increases, the Neel ordered state is stabilized gradually. Moreover, we find power laws at low temperatures: a T-4-law for the spin-wave excitation, and a T-2-law for the sublattice magnetization, which is consistent with the nuclear magnetic resonance experiments on antiferromagnets. The interplanar coupling dependences of the finite-temperature spin-wave excitation and magnetization are also given.