Domain-Wall Motion Driven by Laplace Pressure in Co-Fe- B/MgO Nanodots with Perpendicular Anisotropy

We study the magnetization reversal of Co-Fe-B/MgO nanodots with perpendicular anisotropy of size ranging from w=400 nm to 1 μm. Contrary to previous experiments, the switching field distribution is shifted toward lower magnetic fields as the size of the elements is reduced with a mean switching field varying as 1/w. We show that this mechanism can be explained by the nucleation of a pinned magnetic domain wall (DW) at the edges of the nanodots where damages are introduced by the patterning process. As the surface tension (Laplace pressure) applied on the DW increases when reducing the size of the nanodots, we demonstrate that to reverse the entire elements, the depinning field varies as 1/w. These results suggest that the presence of DWs must be considered in the switching process of nanoscale elements and open a path toward scalable spintronic devices.