Modeling Thick Metal in Forward Volume Spin Wave Transducers

In this paper, theoretical expression for forward volume spin wave (FVSW) transducer radiation resistance is proposed to encompass the effects of transducer metal thickness. This thickness effect results in a reduction of radiation resistance that scales with metal thickness. The reduction in radiation resistance is especially evident in transducers with metal thicknesses approaching the wavelengths of the spin waves launched. A method which decomposes the current source launching spin waves into a series of orthogonal functions that correspond to the FVSW thickness modes is used to evaluate the expression for radiation resistance. Five different spin wave transducers with metal thicknesses of 0.1, 0.3, 0.5, 0.7, and 0.9 micrometer were simulated in HFSS (using a magnetostatic approximation) and their resultant radiation resistances and radiation efficiencies were compared to the theoretical expression.