  The regular array of magnetic particles (magnetic dots) of the form of a
two-dimensional triangular lattice in the presence of external magnetic field
demonstrates complicated magnetic structures. The magnetic symmetry of the
ground state for such a system is lower than that for the underlying lattice.
Long range dipole-dipole interaction leads to a specific antiferromagnetic
order in small fields, whereas a set of linear topological defects appears with
the growth of the magnetic field. Self-organization of such defects determines
the magnetization process for a system within a wide range of external magnetic
fields.
