STRUCTURE AND DYNAMICS OF A SINGLE 2-PI-VBL IN A MAGNETIC DOMAIN-WALL

The dynamics of a single three dimensional 2 pi-vertical Bloch line (2 pi VBL) structure in a domain wall in garnet have been investigated u sing large scale numerical simulations, The domain wall distorts when a 2 pi-VBL is present at equilibrium, For a film thickness of 1.28 mu m, a maximum wall tilt of 400 Angstrom ((-)2 degrees) was found at the 2 pi VBL. The 2 pi VBL longitudinal wall microdeformation is 1.22 mu m, or almost twice the 2 pi VBL width, When fields normal to the film surface are applied, wall and 2nVBL velocities, along with VBL to wall velocity ratio, are calculated, At fields lower than 10 Oe, the veloc ity ratio at dynamic equilibrium is equal to 7.5. It is half the theor etical ratio pi root Q/2 alpha. (Quality factor Q=4.0, damping constan t alpha=0.2) for a periodic chain of pi VBLs. At fields between 10 to 12 Oe, saturation velocities of 10 m/s and 80 m/s are calculated for t he wall and 2 pi VBL respectively. At higher fields, horizontal Bloch lines (HBLs) are nucleated on each side of the 2 pi VBL structure, Bot h the wall and 2 pi VBL velocities decrease along with the velocity ra tio.