Size-dependent spin-wave frequency in ferromagnetic wire-array structures

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Abstract
Spin-wave frequency measurements in ferromagnetic FeNi wire-array structures by Brillouin light scattering (BLS) are reported. The arrays studied were 600 Å thick and had wire widths of between 0.8 and 10 μm, with separations between wires of twice the width. The spin-wave frequencies were measured in the Voigt geometry with an external field applied parallel or perpendicular to the wires. A rapid drop in BLS intensity with decreasing structure size was seen. For the perpendicular field geometry, we observed a decrease in both the surface and first volume-mode frequencies. We show this to be due to static demagnetizing fields. The parallel field case showed a rise in frequency of only the surface mode with decreasing wire size, which we demonstrate to be the effects of oscillating magnetic edge charges.