Ordered growth of magnetic helical structure under the Dzyaloshinskii-Moriya interaction

We numerically investigated the spread of the magnetic helical structure under the Dzyaloshinskii-Moriya interaction (DMI). During the relaxation process from initial perpendicular magnetism, half-vortex structures are first formed by thermal fluctuation at the boundary of the system. Subsequently, the helical structures extend inward to form well-aligned structures that are perpendicular to the boundary line. We obtained a formula that describes the propagation speed of the helical structure, which is proportional to the DMI strength but is not influenced by the strength of the exchange interaction. The final magnetic structure is determined by the shape of the system or the locations of defects. Therefore, magnetic domain patterns could be engineered by controlling the domain seeds through intentional inclusion of sample defects at specific locations.