Fig. 2: 3D magnetic vector tomography of the giant spearhead magnetofossil.

a Trajectory of the vortex core, coloured according to M_z (red positive, blue negative). Circled region highlights the Bloch point, where the vortex core moment changes sign. An expanded view of the magnetisation vector field surrounding the Bloch point is shown inside the circle. b–d M_x, (e–g) M_y and (h-j) M_z components of magnetisation shown at three selected positions along the fossil length. Black arrows in (b) illustrate the vortex structure in the base of the particle (see also Supplemental Movie S1), and a slice through the magnetisation vector field at this position is shown in the expanded region. Solid line in (h) shows the position of the medial domain wall separating regions with opposing M_z. The M_z components in the tip of the particle are reversed with respect to the base, leading to the twisting of the medial wall in (j) (see also Fig. S1).