Exploration of Phase Transition Behaviours and Magnetic Structures in Some Polar Sulphides Containing Diatomic Anions

Ferroelectric materials are utilized in a wide variety of technical applications, such as non-volatile memory devices and capacitors. These materials are required to adopt non-centrosymmetric and polar crystal structures to give net electric polarization. The conventional approach to stabilise ferroelectric structures relies on second-order Jahn-Teller (SOJT) active cations. However, there only exist a limited number of SOJT cations, and their diamagnetic nature means they by themselves do not allow long-range magnetic order as well as the multiferroic behaviour, an important property towards low-energy memory storage device. In this regard, searching for new inversion-symmetry breaking mechanism is necessary. We recently prepard two quasi-low-dimensional sulphides containing diatomic SH anion. Both materials adopt polar crystal structures and one compound contains paramagnetic transition metals. The absence of any SOJT cation in these materials implies their polar symmetries must come from a different origin, and understanding the underlying mechanism is crucial to help further develop new ferroelectric/multiferroic materials.