Formation and control of internal spin-wave channels in arrays of densely packed Permalloy nanowires

Broadband spin-wave spectroscopy is performed on two arrays of long 300-nm-wide Ni20Fe80 wires which exhibit two different edge-to-edge separations a of 700 and 200nm. When the in-plane field H⃗ is applied a few degrees off from the hard axis direction, an intermediate field regime is found where the central region and the edges of a wire are magnetized in different directions. Here, resonances are pronounced and reflect spin waves confined on the sub-100nm scale within a wire. For small a, the confinement effect is found to occur over a broad regime of H. These results are relevant for high-density integration of magnonic waveguides.