Atomic scale symmetry and polar nanoclusters in the paraelectric phase of ferroelectric materials.

The nature of the "forbidden" local- and long-range polar order in nominally non-polar paraelectric phases of ferroelectric materials has been an open question since the discovery of ferroelectricity in oxide perovskites, ABO. A currently considered model suggests locally correlated displacements of B-site atoms along a subset of <111> cubic directions. Such off-site displacements have been confirmed experimentally; however, being essentially dynamic in nature they cannot account for the static nature of the symmetry-forbidden polarization implied by the macroscopic experiments.

Mechanosynthesis of the Whole YBiMnFeO Perovskite System: Structural Characterization and Study of Phase Transitions.

Perovskite BiFeO and YMnO are both multiferroic materials with distinctive magnetoelectric coupling phenomena. Owing to this, the YBi MnFeO solid solution seems to be a promising system, though poorly studied. This is due to the metastable nature of the orthorhombic perovskite phase of YMnO at ambient pressure, and to the complexity of obtaining pure rhombohedral phases for BiFeO-rich compositions.