Direct observation of the spin structures of vortex domain walls in ferromagnetic nanowires

The spin structures of vortex domain walls forming in a ferromagnetic La0.6Sr0.4MnO₃ nanowire have been directly observed using Lorentz microscopy. We visualized the in-plane anisotropic structures, which exhibited twofold rotational symmetry and revealed that the simultaneous reversal of the vortex chirality and the magnetization directions of separated domains occurs at all the pinning sites. The observations indicate that the chirality is determined by the magnetization directions and the magnetic anisotropy induced at the pinning sites.