On the magnetic structure of a hexagonal Ising antiferromagnet

Domain wall free energies are calculated in a hexagonal Ising antiferromagnet and shown to be very small compared with those in an ordinary two-sublattice antiferromagnet. It is suggested that the magnetic structure of its higher temperature ordered phase is one in which many domains are tangled with each other. Some comments are given on experimental results in CsCoCl₃ and CsCoBr₃.