Domain-wall velocity, mobility, and mean-free-path in permalloy films

Domain-wall velocity was measured for vacuum-deposited permalloy films in the thickness range of from 310 to 3000 Å. The dependence of the velocity on drive field amplitude was non-linear for all of the forty-two films. The ν-H characteristics were clearly separated into two regions (low and high field), except for the thick films ( > 2500 Å). The high field regions were fairly linear, and the interpolated lines intersected the axis at much lower fields than the coercive force and often at the origin. The wall mobilities that were determined from the slope of the high field regions were found to be about one third of the mobilities reported by other authors. These were compared with the theoretical value and found to be in fair agreement. As one of the characteristics of wall motion under fields lower than the coercive force, the mean-free-path of a wall was measured as a function of the easy axis field.