Simulation of Bloch Wall Motion
Experimenta1 and computer simulation results for Bloch wall motion are compared. While good agreement is obtained for wall displacement under low drive fields, and for the critical fields for thin samples and/or long drive pulses, discrepancies arise for short pulses and thicker samples. To investigate the latter, simulations were performed for a two-wall configuration, using Slonczewski's equations of wall motion. The results, which reflected the effect of the demagnetizing field, were better than for single-wall simulations, but discrepancies still remain for short pulses and high drive fields; this may be partly due to the assumption of a constant wall width.
Theory of domain-wall motion in magnetic films and platelets
We calculate dynamical properties of plane and cylindrical magnetic domain walls in a uniaxial film or platelet whose plane is perpendicular to the easy axis. First, we calculate the internal structure of a freely moving wall to determine the nonlinear velocity‐momentum relation. Using a Bloch‐line approximation to the kinetic wall energy, we find that stray magnetic fields emanating from surface poles destabilize the structure at a critical velocity Vp, above which uniform motion is not possible. For a plane wall, we have Vp=24γA/hK1/2, where γ is the gyromagnetic ratio, A is the exchange stiffness, h is the film thickness, and K is the anisotropy. This velocity is usually much less than the critical velocity for bulk wall motion derived by Walker. Combination of the velocity‐momentum relation with the conservation of momentum provides a simple method of calculating the time‐dependent velocity in the presence of a small drive field and small viscous damping. For very small drive, the terminal velocity eq...
Structure of Moving Domain Walls in Magnetic Materials
It is shown that in the regions far away from the center of a moving domain wall the distribution of magnetization is the same as in a spin wave of complex wave number. The structure of the moving wall is calculated rigorously for wall velocities v smaller than a certain critical velocity v1. At the critical velocity the derivative of the wall energy with respect to v becomes infinite. The wall mobility in the subcritical region (v < v1) is inversely proportional to the wall energy.