A High Working Temperature Multiferroic Induced by Inverse Temperature Symmetry Breaking

Abstract

Molecular-based multiferroic materials that possess ferroelectric and ferroelastic orders simultaneously have attracted tremendous attention for their potential applications in multiplestate memory devices, molecular switches, and information storage systems. However, it is still a great challenge to effectively construct novel molecular-based multiferroic materials with multifunctionalities. Generally, the structure of these materials possess high symmetry at high temperatures, while processing an obvious order−disorder or displacement-type ferroelastic or ferroelectric phase transition triggered by symmetry breaking during the cooling processes. Therefore, these materials can only function below the Curie temperature (T c ), the low of which is a severe impediment to their practical application. Despite great efforts to elevate T c , designing single-phase crystalline materials that exhibit multiferroic orders above room temperature remains a challenge. Here, an inverse temperature symmetry-breaking phenomenon was achieved in [FPM][Fe 3 (μ 3 -O)(μ-O 2 CH) 8 ] (FPM stands for 3-(3formylamino-propyl)-3,4,5,6-tetrahydropyrimidin-1-ium, which acts as the counterions and the rotor component in the network), enabling a ferroelastoelectric phase at a temperature higher than T c (365 K). Upon heating from room temperature, two-step distinct symmetry breaking with the mm2Fm species leads to the coexistence of ferroelasticity and ferroelectricity in the temperature interval of 365−426 K. In the first step, the FPM cations undergo a conformational flip-induced inverse temperature symmetry breaking; in the second step, a typical ordered−disordered motion-induced symmetry breaking phase transition can be observed, and the abnormal inverse temperature symmetry breaking is unprecedented. Except for the multistep ferroelectric and ferroelastic switching, this complex also exhibits fascinating nonlinear optical switching properties. These discoveries not only signify an important step in designing novel molecular-based multiferroic materials with high working temperatures, but also inspire their multifunctional applications such as multistep switches.

Giant Anisotropic Thermal Expansion Phase Transition of Silver Iodide Anionic Organic–Inorganic Hybrid

“…In the synthesis of 1 and 2 , the 1,4,5,6-tetrahydropyrimidin-1-ium (THPM) cations were formed by the in situ reaction between 1,3-propylenediamine and HCOOH …”

Experimental Observation of the Fully Ferroelectric–Fully Ferroelastic Effect in Multiferroic Hybrid Perovskites

“…Multiferroic was initially coined by Aizu in 1968 with the theoretical identification of 42 species of simultaneously ferroelectric and ferroelastic phase transition . The famous inorganic Gd 2 (MoO 4 ) 3 with the fully ferroelectric–fully ferroelastic effect was predicted and successfully validated in 1968, serving as a typical model for fully multiferroic over subsequent decades. , The characteristic of a type of ferroelectric–ferroelastic crystal is that the concurrent alteration of the polarization vector alongside changes in the strain tensor, and vice versa, is fully ferroelectric and fully ferroelastic. − Capitalizing on these dual ferroic effects, the development of high-precision electronic micropositioners, tunable radio frequency filters, compatible grating devices, and adaptive devices has become feasible. − Furthermore, the synergy between ferroelectricity and ferroelasticity can markedly enhance material physical properties. , For example, You et al reported a hybrid perovskite multiferroic [Me 3 NCH 2 Cl]­CdCl 3 , whose illustrious electromechanical conversion performance has been proven to be closely related to the partial coupling of ferroelectricity and ferroelasticity. , Benefiting from the numerous advantages of intimate interplay between full ferroelectricity and full ferroelasticity, recently, a large amount of studies have focused on exploring multiferroic materials with ferroelectricity and ferroelasticity. − However, constructing ferroelectric that is compatible with ferroelasticity has been a great challenge due to the strict requirements of crystallographic symmetry, reasonable symmetry breaking, and ingenious evolution of lattice parameters. − …”

Tadpole-Like Polar Molecule Encapsulated in a Two-in-One Supramolecular Cage: Molecular Motion, Phase Transition and Ferroelectricity

“…More interestingly, 1 undergoes a ferroelectric phase transition upon cooling. To our knowledge, although various types of molecular ferroelectrics have been explored in recent years, − 1 represents the first example of a clathrate molecular ferroelectric that features a molecule-inclusive supramolecular cage.…”