Giant Hysteretic Single‐Molecule Electric Polarisation Switching above Room Temperature

Abstract

Continual progress has been achieved in information technology through unrelenting miniaturisation of the single memory bit in integrated ferromagnetic, ferroelectric, optical, and related circuits. However, as miniaturisation approaches its theoretical limit, new memory materials are being sought. Herein, we report a unique material exhibiting single-molecule electric polarisation switching that can operate above room temperature. The phenomenon occurs in a Preyssler-type polyoxometalate (POM) cluster we call a single-molecule electret (SME). It exhibits all the characteristics of ferroelectricity but without long-range dipole ordering. The SME affords bi-stability as a result of the two potential positions of localisation of a Tb ion trapped in the POM, resulting in extremely slow relaxation of the polarisation and electric hysteresis with high spontaneous polarisation and coercive electric fields. Our findings suggest that SMEs can potentially be applied to ultrahigh-density memory and other molecular-level electronic devices operating above room temperature.

Structural Characterization of Cerium‐encapsulated Preyssler‐type Phosphotungstate: Additional Evidence of Ce(III) in the Cavity

“…[1][2][3] Among the various POM structures, Preyssler-type phosphotungstates, [P 5 W 30 O 110 M n + (side)(H 2 O)] (15À n)À (M n + = encapsulated cation), [4] have recently attracted significant attention because they are applicable as acid catalysts, [5] antibacterial materials, [6] liposome collapse reagents, [7] proton-conductive materials, [8,9] single-molecule magnetic materials, [10] and single-molecule electret materials. [11] Preyssler-type molecules have a doughnut-shaped structure consisting of five PO 4 tetrahedra surrounded by 30 WO 6 octahedra, and an internal cavity (Figure 1 It is possible to encapsulate one or two cations in the cavity, [12] such as Na + , [13,14] Ag + , [15][16][17] K + , [18][19][20][21] Ca 2 + , [14] Y 3 + , [14] Bi 3 + , [22] and lanthanide [23] and actinide cations. [14,23,24] Selection of the encapsulated cation(s) is one of the most commonly used methods to adjust the properties of Preyssler molecules.…”

Synthesis of Preyssler-Type Phosphotungstate with Sodium Cation in the Central Cavity through Migration of the Ion

“…The Preyssler-type phosphotungstate was first reported by Preyssler in 1970, and it's structure was later revealed by Pope and Jeannin. 4 A Preyssler-type phosphotungstate, [P5W30O110Na(H2O)] 14− , framework has five PO4 tetrahedra surrounded by 30 WO6 octahedra, creating a doughnut-shaped architecture with internal cavities (Fig. 1).…”

“…Preyssler-type compounds can encase different cations such as Ca 2+ , [5][6][7][8] Bi 3+ , 5,6,8 Ag + , 9-11 Y 3+ , [5][6][7] lanthanide cations, 5,6,[12][13][14] actinide cations, 5,7,12,13,15 and K +16-18 in these cavities. In most cases, the cation occupies one of the side cavities and coordinates with a water molecule.…”

Solid‐State Ion Migration in the Preyssler‐Type Phosphotungstate for the Preparation of the Dipotassium Cation‐Encapsulated Derivative

“…POMs have been employed as functional materials in many fields . Among the wide classes of POMs, the Preyssler‐type phosphotungstates, [P 5 W 30 O 110 M x + (side)(H 2 O)] (15– x )– (M = encapsulated cation), have attracted remarkable attention because of their antibacterial activity and applications in acid catalysis, proton‐conductive materials, single‐molecule magnetic materials, and single‐molecule electret materials …”