抄録
Structures of domain walls in the commensurate phase and an order of the incommensurate-commensurate transition in proper ferroelectrics are investigated on the basis of the phenomenological free energy with an elastic term. Apart from the oscillatory domain wall previously found, the domain wall with an exponential decay is shown to exist. The asymptotic interaction between discommensurations is calculated theoretically, and is shown to be attractive, irrespective of the different behaviours of the domain wall. The transition is first-order one, in agreement with the numerical calculation. This differs from the case of improper ferroelectrics, whose transition can be either continuous or discontinuous even when the tail of the domain wall decays monotonically.
