NONLINEAR LOVE WAVES IN A FERROELASTIC FILM ON AN ELASTIC SUBSTRATE

A theory of nonlinear acoustic Love wave propagation in a ferroelastic him on an elastic substrate is presented. The main stress in this wor k is put upon the investigation of the properties of the nonlinear aco ustic 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 pa raelastic-ferroelastic phase transition are estimated for real ferroel ectric films. In the framework of the asymptotic approach the effectiv e nonlinear Schrodinger equation for the envelope of the Love wave is derived and the possibility of bright- and dark-soliton formation is d iscussed. It is demonstrated that for a change of career wave wavenumb er the transition between stable wave propagation and the modulation i nstability is realized. It is found that the strong dispersion of the soft Love wave near the ferroelastic phase transition is responsible f or such a transition.