Structure and dynamics of a single 2/spl pi/VBL in a magnetic domain wall

摘要

The dynamics of a single three dimensional 2/spl pi/-vertical Bloch line (2/spl pi/VBL) structure in a domain wall in garnet have been investigated using large scale numerical simulations. The domain wall distorts when a 2/spl pi/-VBL is present at equilibrium. For a film thickness of 1.28 /spl mu/m, a maximum wall tilt of 400 /spl Aring/ (/spl sim/2/spl deg/) was found at the 2/spl pi/VBL. The 2/spl pi/VBL longitudinal wall microdeformation is 1.22 /spl mu/m, or almost twice the 2/spl pi/VBL width. When fields normal to the film surface are applied, wall and 2/spl pi/VBL 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 /spl pi//spl radic/(Q/2/spl alpha/) (quality factor Q=4.0, damping constant /spl alpha/=0.2) for a periodic chain of /spl pi/VBLs. At fields between 10 to 12 Oe, saturation velocities of 10 m/s and 80 m/s are calculated for the wall and 2/spl pi/VBL respectively. At higher fields, horizontal Bloch lines (HBLs) are nucleated on each side of the 2/spl pi/VBL structure. Both the wall and 2/spl pi/VBL velocities decrease along with the velocity ratio.