Exceptional structural phase transition near room temperature in an organic-inorganic hybrid ferroelectric.

An organic-inorganic hybrid ferroelectric, (C 6 H 5 CH 2 CH 2 NH 3 ) 2 [HgI 4 ], undergoes an exceptional structural phase transition near room temperature, triggered by a flip of half the organic cations and an order-disorder transition of the inorganic anions, and may be regarded as a displacive-type ferroelectric. This finding provides a new structural phase transition mechanism in molecule-based ferroelectrics.