Low-Temperature Behavior of the Anisotropic Heisenberg Antiferromagnet in the Neighborhood of the Magnetic Phase Boundaries

Abstract

Using spin-wave theory, including spin-wave interactions to leading order in $\frac{1}{2S}$, the temperature dependence of the critical magnetic field curves between the antiferromagnetic, the flop, and the paramagnetic phases have been calculated for a Heisenberg antiferromagnet with both uniaxial single-ion anisotropy and anisotropic exchange interaction. The free energy has been obtained for all three phases, and the behavior of the specific heat and the susceptibility in the neighborhood of these phase boundaries as a function of magnetic field for a fixed temperature is discussed in detail.