Molecular orientation dynamics triggers ferroelectricity and ferroelasticity in an organic–inorganic halide material

Abstract

The ability to achieve multiple ferroic orderings can provide more selectivity for diverse applications, such as non-volatile memory, energy conversion, and pressure sensors. Molecular crystals occupy an important position in ferroic materials owing to their structural diversity, ease of preparation, low cost, and mechanical flexibility. However, it has been a great challenge to satisfy multiple ferroic ordering in a single material that is constrained by stringent crystal symmetry requirements. Herein, we have achieved multiple ferroic ordering coexistence in (imidazolium)₃PbBr₅ by utilizing ingenious molecular orientation dynamics. Confined by the unique skeleton of corner-shared lead halide octahedrons, the molecular out-of-plane and in-plane reorientational motions of imidazolium cations modulated by thermal stimulation result in ferroelectric and ferroelastic phase transitions. This study offers instructive clues for designing multiple ferroic orderings in a single material for potential emerging applications.