Dennis Hardt
Domain walls (DWs) describe the transition region between two magnetic domains. In this work, we study these structures in a driven system given by a 1D planar ferrimagnet with anisotropy of the form of a symmetric double-well potential in the z-component of the magnetization. This establishes a Goldstone mode as rotation in the x-y-plane that can be activated by an oscillating magnetic field. We model this via two coupled Langevin equations.
In the noise-free case (T=0), this leads to a spontaneous symmetry breaking, which is evident in the collective movement of all (remaining) DWs in one direction (left or right).
At finite temperature, on the other hand, DW-pairs can also be formed. We observe a competition between the annihilation (by drive) and the creation (by noise) of DWs.
The DWs generated by noise are randomly driven to the left or to the right. This leads to a suppression of the total number of DWs compared to the non-driven thermal case.