The Influence of the internal domain wall structure on spin wave band structure in periodic magnetic stripe domain

The magnetization dynamics in periodic magnetic stripe domain patterns in thin ferromagnetic films is summarized. First, a brief theoretical background of magnetization dynamics and spin wave dynamics in the presence of a single domain wall for various configuration of magnetic domains (in-plane and out-of-plane) and domain walls (Bloch- and Néel-type domain walls) is introduced. Then, spin wave dynamics in periodic stripe magnetic domain pattern is studied on an example of a multilayer system composed of Co/Pd. The considered magnetization configuration is non-collinear across both the domain walls and the film thickness. It has the form of a “corkscrew”-like structure that consists of a Bloch wall in the film's center with two Néel caps at the film's surfaces. All domain walls have the same polarity. The Brillouin light scattering measurements were performed to study magnetization dynamics experimentally, and the results were interpreted with the use of micromagnetic simulations. The periodic arrangement of the magnetization increases the number of spin wave bands similarly like a one-dimensional magnonic crystal. The properties of the dynamical excitation related to translational motion of the domain wall (zero-frequency Goldstone modes) are shown. Further, the dynamics of the magnetization configurations with the same and alternating polarities of the neighboring walls are compared. The magnetization dynamics for the propagation along the domain walls direction is analyzed, as well. Here, the interaction between the walls and nonreciprocal properties result in the formation of unidirectional channels, where waves travel in every second wall in the opposite direction.