Spin waves in magnetic wires: a Brillouin study

A detailed Brillouin light scattering study of the dispersion of surface spin waves in cobalt wires is reported. A comparison with the dispersion curve of the unpatterned continuos film is achieved and the effects of the size-dependent demagnetizing field are discussed. Concerning the pseudo-bulk modes appearing in the patterned film, as expected, their variation is quasi-independent from the variation of the angle of incidence. The experimental Brillouin spectra do not display any splitting of the Damon-Eshbach mode into a set of discrete lines in contrast with previously published results on permalloy. We interpret this difference as arising from the large experimental linewidth combined with the presence of an anisotropy in the case of cobalt. A qualitative model of the scattering intensity is presented in order to illustrate this difference. The involved eigenfrequencies are derived from numerical calculations which also allow us to discuss the relevant quantization conditions of the in-plane wave vector