Interaction between ferroelastic domain walls mediated by thermal fluctuations and defects

Abstract

Abstract Owing to macroscopic elastic fields arising from bending of a ferroelastic domain wall because of thermal fluctuations and defects there appears an attraction between two parallel walls. The attraction energy due to thermal fluctuations decays at large distances between the walls (h) as h−2 with a factor proportional to T. For proper ferroelastics and improper ones with a quadratic dependence of the spontaneous deformation on the order parameter this law is valid for all h greater than the domain wall thickness (which is the minimum length of the problem). The dependence of the attraction energy due to defect-induced bending of the walls is not determined but it is argued that it is power-like. As the repulsion energy has an exponential dependence on h (including the case of defect-induced bending) it is concluded that the ferroelastic-incommensurate transition is discontinuous.