  The influence of magnetic dipole interactions (MDIs) on the magnetic
properties of local-moment spin systems is investigated. The eigenvalues and
eigenvectors of the MDI tensor are determined for a wide variety of spin
lattices and magnetic wavevectors in the magnetically ordered state with
collinear moment alignments. The predicted easy axes in the ordered state are
compared with experimental results for antiferromagnetic (AFM) compounds. The
theory is generalized to include noncollinear AFM structures and compared with
experiments. Many properties caused or influenced by MDIs in the ordered and
paramagnetic states are calculated within Weiss molecular field theory.
