Nonlinear Love waves in a ferroelastic film on an elastic substrate

Abstract

A theory of nonlinear acoustic Love wave propagation in a ferroelastic film on an elastic substrate is presented. The main stress in this work is put upon the investigation of the properties of the nonlinear acoustic waves in films close to the phase transition, which is different from previously reported works on this subject. The parameters of the striction superstructure (elastic domains) nucleating close to the paraelastic - ferroelastic phase transition are estimated for real ferroelectric films. In the framework of the asymptotic approach the effective nonlinear Schrödinger equation for the envelope of the Love wave is derived and the possibility of bright- and dark-soliton formation is discussed. It is demonstrated that for a change of career wave wavenumber the transition between stable wave propagation and the modulation instability is realized. It is found that the strong dispersion of the soft Love wave near the ferroelastic phase transition is responsible for such a transition.