Dynamics of magnetic domain walls with loosely spaced vertical Bloch lines

The dynamics of a magnetic domain wall containing vertical Bloch lines (VBLs) has been investigated using numerical methods. The wall is of the kind found in thin-film materials with a large anisotropy perpendicular to the plane of the film. The VBLs are all of the same chirality and are periodically repeated along the wall at equal spacing. The wall is driven by an applied field perpendicular to the film plane and the VBLs move gyrotropically. Both the wall and VBLs, starting from an equilibrium shape, soon attain a constant velocity. Distortion of the wall and structure from the equilibrium shape is evident and increases with field. The wall and VBL velocity both increase with field but neither are linear so that the ratio of VBL velocity to wall velocity decreases with applied field. For an applied field extrapolated to zero, the wall velocity agrees with the value predicted by the analytical rigid wall model and the ratio decreases by 50% for higher fields because of the distortion