Effect of width and thickness on propagating spin waves in permalloy microstripe waveguides

We report the effect of thickness and width on the spin wave transport and dispersion characteristics of permalloy (Py) microstripes using analytical calculations and experiments. Py waveguides with widths ranging from 2 to 4 μm were fabricated for two different thicknesses: 5 and 20 nm. Our results show a notable increase in the group velocity of spin waves with greater thickness, showing a fourfold rise as the thickness increases. Additionally, the accessible frequency range expands from 0.6 to 2.5 GHz as the thickness increases. We find that the spin wave mode frequency is affected by both thickness and width, with a frequency shift of approximately 0.2 GHz observed when the width increases from 2 to 4 μm. Moreover, spin waves decay more rapidly in thinner films, with the decay length of 20 nm-thick waveguides being four times longer than that of 5 nm-thick waveguides. Thicker and wider waveguides provide a longer decay length, facilitating the transmission of information over longer distances without significant energy loss. Our study offers an understanding of the spin wave propagation in microstrip waveguides and its potential in the development of future magnonic devices.