Manipulation of Three-Dimensional Magnetic Domain Wall Structure

To harness the magnetic textures such as skrymions and vortices in future spintronic devices, it is essential to understand the three-dimensional (3D) magnetic configurations and their topological properties [1-2] which can provide not only the detailed mechanisms of the magnetic texture switching but also an efficient method of the texture state control. One of the typical 3D magnetic configuration is the asymmetric Bloch wall (ABW) which forms at the center of the 180 degree DW of the elongated Landau domain structure in a rectangular patterned thin ferromagnetic film [3-6]. The Landau domain structure consists of two vortex configuration on the bottom and the top surfaces with oppositely shifted core position and thus, the core structure connecting two surface vortices is elongated along the thickness. At the center of this elongated core structure, the ABW is formed. Consequently, the clockwise or counter-clockwise rotating sense of the ABW is determined by the shift direction of the top and bottom surface-vortex cores. Since those two rotating sense states have exactly the same energy, they are degenerate states and they appear at the same probability. To manipulate those states, it is necessary to break the symmetry of two states. For example, asymmetric geometry was utilized for control the ABW states [7]. In this presentation, we propose an efficient way to manipulate the rotating states based on the symmetry breaking of the ABW through the external magnetic field only by using micromagnetic simulations. Furthermore, we successfully verified our method experimentally by using the magnetic transmission soft x-ray microscopy (MTXM)