Giant Hysteretic Single‐Molecule Electric Polarisation Switching above Room Temperature

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 Tb3+ 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.This study was supported by JSPS KAKENHI Grant Numbers JP16H04223, JP16K14101, JP24350095, and JP25220803;the Joint Research Project between JSPS and the National Science Foundation of China (NSFC);and JSPS Core-to-Core Program, A. Advanced Research Networks. This work was also performed under the aegis of the Canon Science Promotion Foundation, Murata Science Foundation, Casio Science Promotion Foundation, and the Cooperative Research Program of “Network Joint Research Centre for Materials and Devices”. M.K. is also funded by CNRS, France.アクセプト後にキーワード・アブストラクト等変更あり

Preparation of Preyssler-type Phosphotungstate with One Central Potassium Cation and Potassium Cation Migration into the Preyssler Molecule to form Di-Potassium-Encapsulated Derivative

A mono-potassium cation-encapsulated Preyssler-type phosphotungstate, [P5W30O110K]14− (1), was prepared as a potassium salt, K14[P5W30O110K] (1a), by heating mono-bismuth- or mono-calcium-encapsulat ed Prey ssler-type p hosphot ungstates (K12[P5W30O110Bi(H2O)] or K13[P5W30O110Ca(H2O)]) in acetate buffer. Characterization of the potassium salt 1a by single-crystal X-ray structure analysis, 31P and 183W nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared spectroscopy, high-resolution electrospray ionization mass spectroscopy, and elemental analysis revealed that one potassium cation is encapsulated in the central cavity of the Preyssler-type phosphotungstate molecule with a formal D5h symmetry. Density functional theory calculations have confirmed that the potassium cation prefers the central position of the cavity over a side position, in which no water molecules are coordinated to the encapsulated potassium cation. 31P NMR and cyclic voltammetry analyses revealed the rapid protonation−deprotonation of the oxygens in the cavity compared to that of other Preyssler-type compounds. Heating of 1a in the solid state afforded a di-K+-encapsulated compound, K13[P5W30O110K2](2a), indicating that a potassium counter-cation is introduced in one of the side cavities, concomitantly displacing the internal potassium ion from the center to a second side cavity, thus providing a new method to encapsulate an additional cation in Preyssler compounds.M.S. is grateful for the A-STEP program of the Japanese Science and Technology Agency (JST), and Furukawa Foundation for the Promotion of Technology. X.L. thanks the Spanish Ministry of Science and Innovation (MICINN) (project CTQ2011-29054-C02-01/BQU), the DGR of the Generalitat de Catalunya (grant no. 2014SGR199), and the XRQTC. This work was also supported by the Center for Functional Nano Oxide at Hiroshima University. M.N.K.W. thanks the Indonesian Endowment Fund for Education (LPDP), Ministry of Finance, Republik Indonesia, for a Ph.D. scholarship

Progressive Transformation between Two Magnetic Ground States for One Crystal Structure of a Chiral Molecular Magnet

We report the exceptional observation of two different magnetic ground states (MGS), spin glass (SG, <i>T</i>_B = 7 K) and ferrimagnet (FI, <i>T</i>_C = 18 K), for one crystal structure of [{Mn^II(<i>D</i>/<i>L</i>-NH₂ala)}₃{Mn^III(CN)₆}]·3H₂O obtained from [Mn­(CN)₆]^3– and <i>D</i>/<i>L</i>-aminoalanine, in contrast to one MGS for [{Mn^II(<i>L</i>-NH₂ala)}₃{Cr^III(CN)₆}]·3H₂O. They consist of three Mn­(NH₂ala) helical chains bridged by M^III(CN)₆ to give the framework with disordered water molecules in channels and between the M^III(CN)₆. Both MGS are characterized by a negative Weiss constant, bifurcation in ZFC-FC magnetizations, blocking of the moments, both components of the <i>ac</i> susceptibilities, and hysteresis. They differ in the critical temperatures, absolute magnetization for 5 Oe FC (lack of spontaneous magnetization for the SG), and the shapes of the hysteresis and coercive fields. While isotropic pressure increases both <i>T</i>_crit and the magnetizations linearly and reversibly in each case, dehydration progressively transforms the FI into the SG as followed by concerted in situ magnetic measurements and single-crystal diffraction. The relative strengths of the two moderate Mn^III–CN–Mn^II antiferromagnetic (<i>J</i>₁ and <i>J</i>₂), the weak Mn^II–OCO–Mn^II (<i>J</i>₃), and Dzyaloshinkii–Moriya antisymmetric (DM) interactions generate the two sets of characters. Examination of the bond lengths and angles for several crystals and their corresponding magnetic properties reveals a correlation between the distortion of Mn^III(CN)₆ and the MGS. SG is favored by higher magnetic anisotropy by less distorted Mn^III(CN)₆ in good accordance with the Mn–Cr system. This conclusion is also born out of the magnetization measurements on orientated single crystals with fields parallel and perpendicular to the unique <i>c</i> axis of the hexagonal space group

Šrámek (Krška): "Stříbrný vítr" on a Silver Screen

in English In my bachelor thesis I compare the novel Stříbrný vítr1 by Czech author Fráňa Šrámek with the movie adaptation made by Czech filmmaker Václav Krška. The most important aspects of Šrámek's novel are: disrupted composition, poetic language and the subject perspective of the main character Jan Ratkin. The composition is formed by the crucial points of the life of Ratkin during his growing up. Šrámek's poetic language is full of metaphors, metonymies and personifications. The most important stylistic feature of the text is its subjectivisation which is used to express the shifts of the mood of the main character. The main topic of the novel is the youth and how it is changed on its way to adulthood. The name of the novel "Stříbrný vítr" is a metaphor for the longing of the main character, who longs to revolt, to love and to know the world. The filmmaker Václav Krška altered both the story and the whole message of Šrámek's piece of art. Krška changed the time frame from thirteen years to one year, therefore the main story is no longer about Ratkin's growing up, but it depicts one year of his almost adult life. Another change was to focus on the love motive while neglecting other motives e.g. Ratkin's revolts and his effort to evolve both sexually and spiritually. The main story is therefore..

Progressive Transformation between Two Magnetic Ground States for One Crystal Structure of a Chiral Molecular Magnet

We report the exceptional observation of two different magnetic ground states (MGS), spin glass (SG, <i>T</i>_B = 7 K) and ferrimagnet (FI, <i>T</i>_C = 18 K), for one crystal structure of [{Mn^II(<i>D</i>/<i>L</i>-NH₂ala)}₃{Mn^III(CN)₆}]·3H₂O obtained from [Mn­(CN)₆]^3– and <i>D</i>/<i>L</i>-aminoalanine, in contrast to one MGS for [{Mn^II(<i>L</i>-NH₂ala)}₃{Cr^III(CN)₆}]·3H₂O. They consist of three Mn­(NH₂ala) helical chains bridged by M^III(CN)₆ to give the framework with disordered water molecules in channels and between the M^III(CN)₆. Both MGS are characterized by a negative Weiss constant, bifurcation in ZFC-FC magnetizations, blocking of the moments, both components of the <i>ac</i> susceptibilities, and hysteresis. They differ in the critical temperatures, absolute magnetization for 5 Oe FC (lack of spontaneous magnetization for the SG), and the shapes of the hysteresis and coercive fields. While isotropic pressure increases both <i>T</i>_crit and the magnetizations linearly and reversibly in each case, dehydration progressively transforms the FI into the SG as followed by concerted in situ magnetic measurements and single-crystal diffraction. The relative strengths of the two moderate Mn^III–CN–Mn^II antiferromagnetic (<i>J</i>₁ and <i>J</i>₂), the weak Mn^II–OCO–Mn^II (<i>J</i>₃), and Dzyaloshinkii–Moriya antisymmetric (DM) interactions generate the two sets of characters. Examination of the bond lengths and angles for several crystals and their corresponding magnetic properties reveals a correlation between the distortion of Mn^III(CN)₆ and the MGS. SG is favored by higher magnetic anisotropy by less distorted Mn^III(CN)₆ in good accordance with the Mn–Cr system. This conclusion is also born out of the magnetization measurements on orientated single crystals with fields parallel and perpendicular to the unique <i>c</i> axis of the hexagonal space group

On the Nature of the Structural and Magnetic Phase Transitions in the Layered Perovskite-Like (CH₃NH₃)₂[Fe^IICl₄]

In view of renewed interest in multiferroic for molecular systems, we re-examine the structural and magnetic properties of the potentially ferroic layered perovskite-like (CH₃NH₃)₂[Fe^IICl₄] due to its high-temperature magnetic ordering transition. The structures from several sets of diffraction data of single crystals consist of square-grid layers of corner-sharing FeCl₆ octahedra and changes from the high-symmetry <i>I</i>4/<i>mmm</i> (<i>T</i> > 335 K) to the low-symmetry <i>Pccn</i> (<i>T</i> < 335 K). In the former the iron and bridging chlorine atoms are within the layer and the organic cations sit in the middle of each square grid, while in the latter the octahedra are tilted in pairs, two in and two out, progressively by up to 12° and the nitrogen atoms follow their motion to be nearer to the two-in pairs. Crystals are stable up to 450 K and display three phase transitions, two structural at 332 and 233 K and one magnetic at 95 K. The temperature dependences of the dc magnetization (zero-field and field-cooling modes) in different applied fields (10–10 000 Oe) on several aligned single crystals independently reveal a hidden-canted antiferromagnetic ground state of at least four sublattices and not the reported canted antiferromagnetic ground state. A metamagnetic critical field of only 200 Oe transforms it to a canted antiferromagnet. The estimated canting angle is 1.4° in zero field, and it folds to ca. 2.8° in a field of 50 kOe at 2 K. The easy axis is along 010, the hard axis is along 100, and the intermediate and canting axis is 001. Using the available extracted parameters the phase diagram has been constructed. This study provides evidence of a complex and intricate manifestation of the orientation, temperature, and field dependence of the interplay between anisotropy and coherent lengths, which would need further studies

On the Nature of the Structural and Magnetic Phase Transitions in the Layered Perovskite-Like (CH₃NH₃)₂[Fe^IICl₄]

In view of renewed interest in multiferroic for molecular systems, we re-examine the structural and magnetic properties of the potentially ferroic layered perovskite-like (CH₃NH₃)₂[Fe^IICl₄] due to its high-temperature magnetic ordering transition. The structures from several sets of diffraction data of single crystals consist of square-grid layers of corner-sharing FeCl₆ octahedra and changes from the high-symmetry <i>I</i>4/<i>mmm</i> (<i>T</i> > 335 K) to the low-symmetry <i>Pccn</i> (<i>T</i> < 335 K). In the former the iron and bridging chlorine atoms are within the layer and the organic cations sit in the middle of each square grid, while in the latter the octahedra are tilted in pairs, two in and two out, progressively by up to 12° and the nitrogen atoms follow their motion to be nearer to the two-in pairs. Crystals are stable up to 450 K and display three phase transitions, two structural at 332 and 233 K and one magnetic at 95 K. The temperature dependences of the dc magnetization (zero-field and field-cooling modes) in different applied fields (10–10 000 Oe) on several aligned single crystals independently reveal a hidden-canted antiferromagnetic ground state of at least four sublattices and not the reported canted antiferromagnetic ground state. A metamagnetic critical field of only 200 Oe transforms it to a canted antiferromagnet. The estimated canting angle is 1.4° in zero field, and it folds to ca. 2.8° in a field of 50 kOe at 2 K. The easy axis is along 010, the hard axis is along 100, and the intermediate and canting axis is 001. Using the available extracted parameters the phase diagram has been constructed. This study provides evidence of a complex and intricate manifestation of the orientation, temperature, and field dependence of the interplay between anisotropy and coherent lengths, which would need further studies

Progressive Transformation between Two Magnetic Ground States for One Crystal Structure of a Chiral Molecular Magnet

We report the exceptional observation of two different magnetic ground states (MGS), spin glass (SG, <i>T</i>_B = 7 K) and ferrimagnet (FI, <i>T</i>_C = 18 K), for one crystal structure of [{Mn^II(<i>D</i>/<i>L</i>-NH₂ala)}₃{Mn^III(CN)₆}]·3H₂O obtained from [Mn­(CN)₆]^3– and <i>D</i>/<i>L</i>-aminoalanine, in contrast to one MGS for [{Mn^II(<i>L</i>-NH₂ala)}₃{Cr^III(CN)₆}]·3H₂O. They consist of three Mn­(NH₂ala) helical chains bridged by M^III(CN)₆ to give the framework with disordered water molecules in channels and between the M^III(CN)₆. Both MGS are characterized by a negative Weiss constant, bifurcation in ZFC-FC magnetizations, blocking of the moments, both components of the <i>ac</i> susceptibilities, and hysteresis. They differ in the critical temperatures, absolute magnetization for 5 Oe FC (lack of spontaneous magnetization for the SG), and the shapes of the hysteresis and coercive fields. While isotropic pressure increases both <i>T</i>_crit and the magnetizations linearly and reversibly in each case, dehydration progressively transforms the FI into the SG as followed by concerted in situ magnetic measurements and single-crystal diffraction. The relative strengths of the two moderate Mn^III–CN–Mn^II antiferromagnetic (<i>J</i>₁ and <i>J</i>₂), the weak Mn^II–OCO–Mn^II (<i>J</i>₃), and Dzyaloshinkii–Moriya antisymmetric (DM) interactions generate the two sets of characters. Examination of the bond lengths and angles for several crystals and their corresponding magnetic properties reveals a correlation between the distortion of Mn^III(CN)₆ and the MGS. SG is favored by higher magnetic anisotropy by less distorted Mn^III(CN)₆ in good accordance with the Mn–Cr system. This conclusion is also born out of the magnetization measurements on orientated single crystals with fields parallel and perpendicular to the unique <i>c</i> axis of the hexagonal space group