Flux Reversal by Néel Wall Motion

Abstract

Domain wall motion is expected to be the fundamental flux reversal mechanism for thin permalloy films in the low drive region HK. The velocity of a wall when a switching field H is applied is given by V=G(H‐H₀), where G is the mobility and H₀ is the starting field. For films with thicknesses on the order of few hundred angstroms, where Néel walls are expected, the mobility is limited by intrinsic damping to a value much smaller than would be expected if only eddy current damping were present. Calculations have been made using a value for the damping constant, α=.015, obtained from coherent rotation studies, and the experimental values for the thickness of the wall obtained by Fuchs in order to obtain G as a function of film thickness. The mobility was measured for seven permalloy films ranging from 128 to 495Å thick. The agreement between the calculations and experiment was within 30%, indicating that the value of α for a 100‐Å film is nearly the same as for thicker films.