Resonance modes of magnetically generated surface waves in acoustic wave guide systems

Acoustic resonances were modelled in magnetostrictively activated surface acoustic wave devices. The devices consisted of a substrate with a thin magnetic film and patterned electrodes. The finite element model was verified against experimental results of two different device length scales. Optical and electrical measurements showed resonances at the same frequencies. One group of devices had an electrode centre to centre distance of 300 mu m and showed resonances in the range 10-30 MHz in contrast to the other group with a 10th of that electrode feature. Acoustic modes were identified and Rayleigh velocities were calculated. The model agrees well with devices on glass substrates, whereas devices on silicon substrates require careful consideration of material parameters due to the anisotropic mechanical characteristics of silicon.