Random electric field instabilities of relaxor ferroelectrics

Relaxor ferroelectrics are complex oxide materials which are rather unique to study the effects of compositional disorder on phase transitions. Here, we study the effects of quenched cubic random electric fields on the lattice instabilities that lead to a ferroelectric transition and show that, within a microscopic model and a statistical mechanical solution, even weak compositional disorder can prohibit the development of long-range order and that a random field state with anisotropic and power-law correlations of polarization emerges from the combined effect of their characteristic dipole forces and their inherent charge disorder. We compare and reproduce several key experimental observations in the well-studied relaxor PbMg1/3Nb2/3O3–PbTiO3. A microscopic model shows how compositional disorder in the form of quenched random electric fields acting in concert with dipolar interactions prohibit long-range ordering in relaxor ferroelectrics. Relaxor ferroelectrics are a class of complex oxides with perovskite structure that exhibit several properties that make them attractive candidates for energy harvesting and storage. And although it is thought that the random electric fields that arise from compositional disorder play an important role in relaxor ferroelectricity, there is no consensus on a theoretical description. Jose R. Arce-Gamboa and Gian G. Guzman-Verri from the University of Costa Rica and Argonne National Laboratory have developed a microscopic model that shows how a metastable random fluctuation state can form that has no long range ordering, which highlights the important role of quenched random fluctuations and also of dipolar forces on relaxor behavior.