Channeling of magnetostatic surface waves by decoration of ferrite films with metals

Background and Objectives: One of the main tasks for developing magnonic devices is to form and control spin wave beams. For this purpose, the decoration of ferrite films with magnetic or non-magnetic metal areas can be used. The aim of this work is to study the peculiarities of magnetostatic surface wave (MSSW) propagation in the channels formed in yttrium-iron garnet (YIG) films by deposition of 1.5 $\mu$m thick metal decorations from chromium (Cr) and permalloy (Py). Materials and Methods: Studied samples were fabricated on the base of 6.5 $\mu$m-thick epitaxial YIG film by the DC magnetron sputtering, photolithography, and ion etching techniques. Frequency dependencies of magnitude and phase of the transmitted MSSW signal at different applied magnetic field were measured with the help of a vector network analyzer and a microwave probe station. Calculation of the dispersions and insertion losses for MSSW propagating in the metallized YIG film was performed on the basis of Maxwell's equations in the magnetostatic approximation, the Landau-Lifshitz equation, and standard electrodynamic boundary conditions. Results and Conclusion: The optimal channel width w relative to the antenna aperture providing channeling of the MSSW signal with the possibility of "antireflective effect" for the transmitted signal has been found to be w = 200 $\mu$m. It has been shown that for the formation of channeling effect, one needs to use a non-magnetic metal with the thickness leading to a transition to the "metallic" branch of the MSSW dispersion or a magnetic metal with the thickness resulting in bending of a short-wavelength part of MSSW dispersion. For the studied samples, it is d(Cr) = 1.5 $\mu$m and d(Py) = 30 nm, respectively. The obtained results demonstrate the possibility of using the channels in metallic decorations for the formation of directed spin wave beams.