Brillouin light scattering study of the spin dynamics in nanoscale permalloy stripes: Theory and experiment

The spin-wave modes in nanoscale permalloy stripes are studied using Brillouin light scattering for the case where an external magnetic field is applied transversely to the length of the stripes. By adjusting the magnitude of this external field, the overall magnetization may be varied between the approximately transverse and longitudinal orientations. The observed spin-wave frequencies are analysed using a recently developed microscopic dipole-exchange theory that is particularly appropriate when the magnetization displays strong spatial inhomogeneity. Comparison between theory and experiment for the two sizes of stripes studied gives fairly good agreement, allowing the magnetic parameters of permalloy to be deduced. A small magnetic anisotropy of the easy-plane type is shown to play an important role. & 2008 Elsevier Ltd. All rights reserved.