Systematic survey of magnetic configurations in multilayer ferromagnet system with dipole-dipole interaction

We investigate various magnetic configurations caused by the dipole--dipole interaction in thin-film magnets with perpendicular anisotropy under open boundary conditions. Two different approaches are simulated: one starts from a random magnetic configuration and decreases temperatures stepwisely; the other starts from the saturated out-of-plane ferromagnetic state to evaluate its metastability. As typical patterns of magnetic configuration, five typical configurations are found: an out-of-plane ferromagnetic, in-plane ferromagnetic, vortex, multidomain, and canted multidomain states. Notably, the canted multidomain forms a concentric magnetic-domain pattern with an in-plane vortex structure, resulting from the open boundary conditions. Concerning the coercivity, a comparison of the magnetic configurations in both processes reveals that the out-of-plane ferromagnetic state exhibits metastability in the multidomain state, but not in the vortex state. We also confirm that the so-called Neel-cap magnetic-domain-wall structure, which is originally discussed in the in-plane anisotropy system, appears at the multidomain state.