Sub-micrometer near-field focusing of spin waves in ultrathin YIG films

Abstract

We experimentally demonstrate tight focusing of a spin wave beam excited in extended nanometer-thick films of yttrium iron garnet by a simple microscopic antenna functioning as a single-slit near-field lens. We show that the focal distance and the minimum transverse width of the focal spot can be controlled in a broad range by varying the frequency/wavelength of spin waves and the antenna geometry. The experimental data are in good agreement with the results of numerical simulations. Our findings provide a simple solution for the implementation of magnonic nanodevices requiring a local concentration of the spin-wave energy.