Structure and dynamics of a single 2πVBL in a magnetic domain wall

The dynamics of a single three dimensional 2π-vertical Bloch line (2πVBL) structure in a domain wall in garnet have been investigated using large scale numerical simulations. The domain wall distorts when a 2π-VBL is present at equilibrium. For a film thickness of 1.28 μm, a maximum wall tilt of 400 Å (~2°) was found at the 2πVBL. The 2πVBL longitudinal wall microdeformation is 1.22 μm, or almost twice the 2πVBL width. When fields normal to the film surface are applied, wall and 2πVBL velocities, along with VBL to wall velocity ratio, are calculated. At fields lower than 10 Oe, the velocity ratio at dynamic equilibrium is equal to 7.5. It is half the theoretical ratio π√(Q/2α) (quality factor Q=4.0, damping constant α=0.2) for a periodic chain of πVBLs. At fields between 10 to 12 Oe, saturation velocities of 10 m/s and 80 m/s are calculated for the wall and 2πVBL respectively. At higher fields, horizontal Bloch lines (HBLs) are nucleated on each side of the 2πVBL structure. Both the wall and 2πVBL velocities decrease along with the velocity ratio