Phase transitions in the canted antiferromagnet

We have made a theoretical study of the transitions induced by a magnetic field for the two-sublattice canted antiferromagnet at 0 K. The Hamiltonian for the system includes isotropic and anisotropic exchange, uniaxial single-ion anisotropy, and Dzyaloshinsky-Moriya D . S-1 X S-2 antisymmetric exchange. The problem is solved in the molecular-field approximation with D perpendicular to the antiferromagnetic easy axis. The equations of equilibrium and stability are solved numerically by computer. The antiferromagnetic to spin-flop transition occurs when the net moment reaches a critical angle alpha(sh)(h(D)). The paramagnetic transition is destroyed by the Dyzaloshinsky-Moriya (DM) interaction unless the field is applied,parallel to D. For H not parallel to D, we observe a quasiparamagnetic transition which manifests itself as an inflection point in the susceptibility.