Magnetic-field dependence of spin waves in ordered permalloy nanowire arrays in two dimensions

Abstract

The longitudinal magnetic-field dependence of quantized spin waves in ordered permalloy nanowire arrays in two dimensions (2D) has been studied by Brillouin spectroscopy. The results were analyzed on the basis of collective spin waves in a hexagonal 2D nanowire array and compared with the results obtained from an analysis of spin waves in an isolated wire. It is found that only the lowest-frequency spin-wave mode of an isolated nanowire is marginally influenced by the presence of neighboring nanowires. These findings are significant for the theoretical understanding and the future technological utilization of magnetic nanowires.

Spin waves in permalloy nanowires: The importance of easy-plane anisotropy

“…In particular, in the case of a small transverse applied field we observe a low-frequency branch in the SW spectrum that is absent in the longitudinal-field studies for permalloy nanowires 10 and that also has no counterpart in the corresponding measurement for nickel. 8 As the magnitude of the transverse field is increased, a SW hybridization ͑or mixing͒ effect is seen for permalloy in the vicinity of the switching field.…”

“…The magnetization and the exchange stiffness parameters, as well as the gyromagnetic ratio, of Ni 80 Fe 20 nanowires are those previously deduced in Ref. 10, namely M s = 0.0645 T, D = 9.30 T nm 2 , and g B = 29.4 GHz/ T, and are not adjusted here. As noted before, they differ in some cases from those of bulk permalloy and were obtained by fitting the experimental data with the macroscopic theory of Ref.…”

“…1. Spectra recorded in the longitudinal field orientation also each contain two magnon peaks, 10 but in this case the peaks are well separated. The spectral peaks were fitted with a Lorentzian function, and the variations of the fitted SW frequencies with transverse and longitudinal magnetic fields are displayed in Figs.…”

“…Investigation of the quantized SW modes by Brillouin light scattering ͑BLS͒ can be useful in probing many properties of these systems such as exchange stiffness, anisotropy terms, dipolar coupling between elements, inhomogeneity of the internal field, etc. [3][4][5][6][7][8][9][10] Other experiments on the SWs in spatially confined magnets have utilized ferromagnetic resonance ͑FMR͒ ͑Ref. 11͒ and time-resolved Kerr microscopy.…”

Dipole-exchange spin waves in ferromagnetic stripes with inhomogeneous magnetization

“…The material parameters employed for this structure are quoted as M s = 0.0645 T and g B = 29.3 GHz/ T, 6 while we take D = 9.30 T nm 2 as in Ref. 20. Also in this case, for a proper comparison between theory and experiment, we allow for the possible effect of single-ion anisotropy on the SW frequencies.…”