Metastable states, spin–reorientation transitions, and domain structures in planar hexagonal antiferromagnets

Equilibrium states are calculated for a planar hexagonal antiferromagnet in a magnetic field oriented in the basal plane. As the field is rotated in the basal plane, a number of first-order phase transitions accompanied by magnetization jumps are observed in the range of metastable states in the system. The range and equilibrium parameters of the thermodynamically stable domain structure formed in the vicinity of such transitions are determined. Magnetization curves in RbMnCl3 are analyzed.