Fig. 2. Occurrence frequency distribution of the femtosecond laser pulse–induced magnetic structures in three geometrical Py disks.

(A to C) Frequency distribution of the femtosecond laser pulse (fluence of 12 mJ/cm²)–induced spin configurations in circular, square, and triangular Py disks, respectively. The bottom panel in each subfigure shows the typical Fresnel images of the experiments, and the middle panel schematically shows their corresponding spin configurations. The most frequent single clockwise and counterclockwise vortex structures with opposite Lorentz imaging contrast were counted separately, while the other magnetic structures with opposite Lorentz imaging contrast but with the same spin configuration were added together. The inset in each subfigure denotes the femtosecond laser pulse quenching process in the Py disks.