Fig. 2

Different types of single-Bloch point (BP) core structures. a–d Single-BP core structures with different magnetic configurations, referred to as type I (a), type II (b), type III (c), and type IV (d). The zoomed-in magnetic transmission soft X-ray microscopy (MTXM) images for BP core structures together with simulated images are shown in the first and the second columns (scale bars: 150 nm), respectively. The boundaries between the black and white contrasts are outlined by the red, turquoise, and blue dotted lines. The simulated internal structures are shown in the third column (scale bar: 50 nm), and the configurations of the BPs contained in the vortex core structures are shown in the fourth column. The yellow line outline the central plane in the disk. The categorization is based on the polarizations of the cores on the top surface and bottom surface of the disk, volumes of cores, and the location of the BP