Dynamical Behaviour of Displacive-Type Ferroelectrics near the Transition Point

Abstract

Dynamical behaviour of both optical and acoustic modes near the transition point of displacive-type ferroelectrics such as BaTiO₃ and SrTiO₃ is investigated theoretically with the use of the correlation function method. Particular attention is paid to the behaviour concerning the memory effect due to the critical fluctuation of polarizations and the possibility of existence of a new-type oscillation peculiar to the critical regime is shown adopting the Silverman Hamiltonian. The dynamic scaling law in the original form is shown not to be applicable to these substances and its physical origin is clarified. An extended form of this law is given.