Pseudoferroelectricity: A possible scenario for doped ZnO

A phenomenological Landau-theory model, where a crystal on cooling from a state with polar symmetry exhibits a maximum of dielectric permittivity and polarization-field hysteresis loops, is offered. The model is equivalent to that of a true ferroelectric in a weak external dc bias. Permittivity maximum occurs as a result of crossing the Widom line. In the model, the role of the external bias plays an intrinsic internal bias originating from a weak polarity of the high temperature state of the material. The results obtained show that the ferroelectriclike phenomena reported for doped ZnO are compatible with a Landau-theory description.