Phase Transitions in the Canted Antiferromagnet

Abstract

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·${\mathrm{S}}_1$×${\mathrm{S}}_2$ 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 ${\alpha }_{\mathrm{sh}}\left(h_D\right)$. 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.