DESIGN METHODOLOGY FOR TUNABLE SAW DEVICES USING MAGNETOSTRICTIVE THIN FILMS.

A simple formulation is developed which is useful for the approximate design of tunable SAW devices using magnetostrictive thin films. The formulation, based on perturbation theory, relates the maximum velocity change or tunability range to the frequency of operation, film thickness, elastic properties of the film and substrate, and magnetic properties of the film. Iron-terbium-boron films deposited on quartz and lithium niobate substrates were used to verify the formula. A significant variability in the magnetic properties of the films were obtained by varying the amount of terbium (0-5 at. %) in the films (80% Fe and 15-20% B). Other films including Fe-Tb, Fe-Si, Fe-B, Co-Cr, and Ni, which were studied by other investigators, were also used to check the formulation.