Simulation of three-dimensional nonperiodic structures of π-vertical Bloch line and 2π-vertical Bloch line in magnetic garnet

Abstract

The dynamics of three-dimensional nonperiodic structures in magnetic garnet have been investigated using large scale numerical simulations. The width of a single π-vertical Bloch line (πVBL) at equilibrium has been measured to be twice the analytical Bloch line width π(A/2πMs2)1/2, where A is the exchange energy constant and Ms the spontaneous magnetization. A 2πVBL has been shown to be 1.5× wider than a πVBL. A comoving technique is used to track a single domain wall with a single π-VBL when a 5 Oe field is applied perpendicularly to the surface of the film. At dynamic equilibrium, the VBL to wall velocity ratio is equal to ten, smaller than the value found for a simulated loosely spaced chain of πVBLs. A 2πVBL is split into two single πVBLs when an in-plane field is applied in the same direction as that of the center spin of the 2πVBL. No motion of the surface spins is observed for the first 10 ns when a 30 Oe field is applied although considerable spin distortion occurs in the wall center. When the field is turned off after 8 ns, the relaxing distortion drives the surface spins apart. The containment due to 2π horizontal Bloch line formation during the process is demonstrated. © 1996 American Institute of Physics.