Symmetry broken is one of most fundamental elements that consist of the paradigm of emergent physical sciences as addressed by Nobel Laureate P.W. Anderson. The general known ferroic orders include ferromagnetic, ferroelectric and ferroelastic orders, which breaks time reversal symmetry, space reversal symmetry and preserves both time and space reversal symmetries, respectively, as shown in Figure.
In the regard of symmetry transformation properties, there should be one more ferric order in the ferro symmetry jigsaw, i.e. ferrotoroidicity which violates both time- and space-reversal symmetries. Due to the special symmetry broken, there exist strong magnetoelectric coupling in ferrotoroidic materials, leading to promising applications in future quantum information technology.
Prof. Changqing Jin's team at IOPCAS recently discovered such a model-holding new compound Ba6Cr2S10. Prof. Xiancheng Wang and Dr. Jun Zhang et.al of the team synthesized the new compound using high pressure technique. It was found that Ba6Cr2S10 consists of well separated dimerized face sharing CrS6 octahedral chains. In the magnetic ordered state the spins are coupled antiferromagnetically along the chain direction. The combination of dimerization and antiparallel spin arrangement in the chain breaks both time- and space-reversal symmetries. The ferroelectricity was observed to coincide with the spin order due to the break of space-reversal symmetry. These results demonstrate that the 1dimensional ferrotoroidic model predicted by theory has been realized in the real material of Ba6Cr2S10. As a rare model-holding ferrotoroidic candidate, the new compound can be considered "a starting point for the further exploration of the physics and applications of ferrotoroidicity, promising to future quantum information technology" report scientists Changqing JIN, Xiancheng Wang, & Jun Zhang.
The work was jointly performed in collaboration with researchers from University College London, Rutherford Appleton Laboratory, Max Plank Institute for Chemical Physics of Solids etc. The study entitled "A ferrotoroidic candidate with well-separated spin chains" was published on Advanced Materials 34, 2106728(2022) at https://doi.org/10.1002/adma.202106728. The study was supported by the National Science Foundation & the Ministry of Science and Technology of China.