ELECTROACOUSTIC SAW INTERACTION IN STRONTIUM-TITANATE

This paper deals with a theoretical investigation into the influence o f external electric fields with varying: orientation on the velocity o f Rayleigh surface acoustic waves (SAW) for (001), (110), and (111) cr ystallographic planes. The contribution of different nonlinear effects to the SAW velocity variation under the action of external fields is analyzed both for a mechanically squeezed and for a free crystal state . Nonlinear electrostriction has been found to contribute more substan tially to the variation of SAW velocity than linear electrostriction. It turns out that because of the linear electrostriction, an external field always provides a greater SAW velocity for all directions of pro pagation and orientations of saggital plane and the inclusion of nonli near electrostriction for many propagation directions causes the SAW v elocity to decrease. The greatest SAW velocity variation is shown to b e 0.016% for the [1 (1) over bar 0] propagation direction in!he (110) metallized plane at E = 20 kV/cm (E parallel to[110]), i.e., two to th ree times magnitude less than the appropriate variation of the bulk ac oustic wave velocity. Theoretical conclusions are in agreement with ex perimentally found dependences.