Mapping Magnetization States in Ultrathin Films with Dzyaloshinskii-Moriya Interaction

To succeed in the next generation of magnetic storages, nanomagnetic structures must be engineered to allow modulation of magnetization amplitude and spatial period. We demonstrate computationally how magnetic nanostructures states (domains with narrow wall, skyrmions, spin spirals, conical spin spirals, and in-plane magnetization configuration) can be designed in ultrathin films with a Dzyaloshinskii-Moriya interaction (DMI) by adjusting two material parameters: perpendicular magnetic anisotropy characterized by the quality factor Q, and reduced DMI constant Delta. For a broad range of Q and Delta parameters, the magnetization states are mapped in (Q, Delta) diagrams and characterized by the periodicity (p) of spatial distribution of magnetization and the mean value of the square of an out-of-plane normalized magnetization component < m(z)(2)>. We explain the transitions between different magnetization states and describe phase transition curves in terms of vanishing of the domain wall energy for both 0 <= Q < 1 and Q > 1 cases. We show that by changing A and/or Q and approaching the phase transition curves, the discontinuous transitions accompanied by jumps of both period and amplitude take place.