Ising metamagnets and their ferroelectric analogs are excellent systems in which to study the effects of frustration. Even very small further-neighbor interactions are shown to lead to new modulated phases, instead of phase separation. If the spins lie in the ferromagnetically coupled planes, the dipole coupling is an example of such an interaction. If the spins are perpendicular to the planes, macroscopic arrays of alternating paramagnetic and antiferromagnetic regions can occur. These are similar to the domain patterns found in dipolar-coupled, uniaxial ferromagnets.

• Received 13 October 1983

DOI:https://doi.org/10.1103/PhysRevB.29.2644