Various Topological Spin Textures in a Two-Dimensional Heisenberg Ferromagnet with Dipole-Dipole Interactions

Magnetic skyrmions are known to exist in ferromagnetic films with dipole-dipole interactions. A two-dimensional Heisenberg ferromagnet with magnetic anisotropy and dipole-dipole interactions is investigated numerically. There exist various topological spin textures. Antiskyrmions coalesce to form spin textures with Q = 2 and 3, where Q is the topological number. Skyrmion molecules and antiskyrmion molecules as well as donut-shaped spin textures with Q = 0 appear. The appearance of these (meta)stable topological spin textures depends on the values of temperature and (or) external magnetic field.