217 results on '"Hiroki Akutsu"'
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2. A 2D Interactive Spin Ladder System, δ′-(BEDT-TTF)2ClC2H4SO3·H2O
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Hiroki Akutsu, Scott S. Turner, and Yasuhiro Nakazawa
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General Materials Science ,General Chemistry ,Condensed Matter Physics - Published
- 2022
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3. Magnetic field induced transition in the charge-glass former θ−(BEDT−TTF)2CsCo(SCN)4
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Tetsuya Nomoto, Satoshi Yamashita, Hiroki Akutsu, and Yasuhiro Nakazawa
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- 2023
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4. Thermodynamic Properties of the Mott Insulator-Metal Transition in a Triangular Lattice System Without Magnetic Order
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Emre Yesil, Shusaku Imajo, Satoshi Yamashita, Hiroki Akutsu, Yohei Saito, Andrej Pustogow, Atsushi Kawamoto, and Yasuhiro Nakazawa
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Condensed Matter - Strongly Correlated Electrons ,Condensed Matter - Materials Science ,Strongly Correlated Electrons (cond-mat.str-el) ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences - Abstract
The organic system, $\kappa$-[(BEDT-TTF)$_{1-x}$(BEDT-STF)$_x$]$_2$Cu$_2$(CN)$_3$, showing the Mott transition between a nonmagnetic Mott insulating (NMI) state and a Fermi liquid (FL), is systematically studied by calorimetric measurements. An increase of the electronic heat capacity at the transition from the NMI state to the FL state which keeps the triangular dimer lattice demonstrates that the charge sector lost in the Mott insulating state is recovered in the FL state. We observed that the remaining low-energy spin excitations in the Mott insulating state show unique temperature dependence, and that the NMI state has a larger lattice entropy originating from the frustrated lattice, which leads to the Pomeranchuk-like effect on the electron localization. Near the Mott boundary, an unexpected enhancement and magnetic-field dependence of heat capacity are observed. This anomalous heat capacity is different from the behavior in the typical first-order Mott transition and shows similarities with quantum critical behavior. To reconcile our results with previously reported scenarios about a spin gap and the first-order Mott transition, further studies are desired., Comment: 9 pages, 4 figures
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- 2023
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5. Thermal conductivity measurement system for molecules-based compounds available in a wide temperature region
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Luming Zhang, Tetsuya Nomoto, Satoshi Yamashita, Hiroki Akutsu, Alexander I. Krivchikov, and Yasuhiro Nakazawa
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Physics and Astronomy (miscellaneous) ,General Physics and Astronomy - Abstract
The construction of a thermal conductivity measurement system designed for tiny molecules-based compounds is reported. We introduce complementary usage of chip-type RuO2 thermometers and E-type thermocouples in the sample part by using thin (ϕ 13μm) constantan and chromel wires. Two pairs of the constantan and chromel wires are used as lead wires for the four-terminal measurement of the resistance of RuO2 thermometers in the low-temperature region below about 20 K. Also, in the higher temperature region above 10 K up to room temperature with the overlapping range of 10-20 K, they are used as thermocouples for detecting temperature differences from that of the heat sink. We also compare a kind of resolution parameter of several sensors as a function of temperature to discuss the rational reason to select suitable sensors depending on the temperature region. Using the constructed apparatus, we report temperature dependences of the thermal conductivity of deuterated κ-(d8:BEDT-TTF)2Cu[N(CN)2]Br in a wide temperature range between 2 and 250 K. The result provides convincing evidence for the validity of the newly developed system for the thermal measurements of molecular crystals.
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- 2023
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6. Asymmetric N-heteroacene tetracene analogues as potential n-type semiconductors
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Andrew J. P. White, Mark Oxborrow, Max Attwood, Anthony Maho, Wern Ng, Sandrine Heutz, Joseph H. L. Hadden, Hao Wu, Hiroki Akutsu, Dong Kuk Kim, Engineering & Physical Science Research Council (EPSRC), and Engineering & Physical Science Research Council (E
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Technology ,Materials science ,Materials Science ,Heteroatom ,Materials Science, Multidisciplinary ,Crystal structure ,Physics, Applied ,ACENES ,chemistry.chemical_compound ,Materials Chemistry ,Molecule ,Thin film ,0912 Materials Engineering ,HOMO/LUMO ,0306 Physical Chemistry (incl. Structural) ,PENTACENE ,Science & Technology ,CRYSTAL ,DERIVATIVES ,Physics ,SUBSTITUTION ,0303 Macromolecular and Materials Chemistry ,General Chemistry ,STATE ,Organic semiconductor ,Crystallography ,Tetracene ,chemistry ,Physical Sciences ,THIN-FILM TRANSISTORS ,Single crystal - Abstract
In the search for high performance n-type organic semiconductors (OSCs) a simple strategy might be substitution of aromatic CH groups for nitrogen heteroatoms. Here, we report the synthesis and characterisation of two novel N-heteroacene compounds, namely, 1,5,12-triazatetracene (TrAT1) and 2,5,12-triazatetracene (TrAT2). Their potential as n-type materials is evaluated against 5,12-diazatetracene (DAT) by UV/vis and EPR spectroscopy, cyclic voltammetry, DFT, single crystal X-ray diffraction and thin film characterisation. Increasing the number of N-heteroatoms was found to stabilise the HOMO and LUMO leading to electron affinities for TrAT1 and TrAT2 of ca. −4 eV. Both compounds were found to exhibit columns of co-facial π-stacked molecules. For TrAT1, molecules are also linked by hydrogen bonding, while the crystal structure of TrAT2 was found to be inherently disordered. Thin films of DAT, TrAT1 and TrAT2 were grown by organic molecular beam deposition (OMBD) and found to form discontinuous films, where TrAT1 exhibited a preferential orientation.
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- 2021
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7. Electric dipole induced bulk ferromagnetism in dimer Mott molecular compounds
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Reizo Kato, Yasuhiro Nakazawa, Hiroki Akutsu, Ryo Yoshimoto, Takehito Nakano, Yugo Oshima, Tetsuro Kusamoto, Hiroshi Yamamoto, and Satoshi Yamashita
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Materials science ,Science ,02 engineering and technology ,Electron ,01 natural sciences ,Article ,Magnetization ,Condensed Matter::Materials Science ,Magnetic properties and materials ,0103 physical sciences ,Antiferromagnetism ,010306 general physics ,Multidisciplinary ,Condensed matter physics ,Mott insulator ,021001 nanoscience & nanotechnology ,Magnetic field ,Dipole ,Ferromagnetism ,Medicine ,Condensed Matter::Strongly Correlated Electrons ,0210 nano-technology ,Ground state - Abstract
Magnetic properties of Mott–Hubbard systems are generally dominated by strong antiferromagnetic interactions produced by the Coulomb repulsion of electrons. Although theoretical possibility of a ferromagnetic ground state has been suggested by Nagaoka and Penn as single-hole doping in a Mott insulator, experimental realization has not been reported more than half century. We report the first experimental possibility of such ferromagnetism in a molecular Mott insulator with an extremely light and homogeneous hole-doping in π-electron layers induced by net polarization of counterions. A series of Ni(dmit)2 anion radical salts with organic cations, where dmit is 1,3-dithiole-2-thione-4,5-dithiolate can form bi-layer structure with polarized cation layers. Heat capacity, magnetization, and ESR measurements substantiated the formation of a bulk ferromagnetic state around 1.0 K with quite soft magnetization versus magnetic field (M–H) characteristics in (Et-4BrT)[Ni(dmit)2]2 where Et-4BrT is ethyl-4-bromothiazolium. The variation of the magnitude of net polarizations by using the difference of counter cations revealed the systematic change of the ground state from antiferromagnetic one to ferromagnetic one. We also report emergence of metallic states through further doping and applying external pressures for this doping induced ferromagnetic state. The realization of ferromagnetic state in Nagaoka–Penn mechanism can paves a way for designing new molecules-based ferromagnets in future.
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- 2021
8. Structural, magnetic and Mössbauer spectroscopic studies of the [Fe(3-bpp)2](CF3COO)2 complex: role of crystal packing leading to an incomplete Fe(<scp>ii</scp>) high spin ⇋ low spin transition
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Djulia Onggo, Varimalla Raghavendra Reddy, Hiroki Akutsu, Ashis Bhattacharjee, Yasuhiro Nakazawa, Hari Sutrisno, and Kristian Handoyo Sugiyarto
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Diffraction ,Materials science ,Transition temperature ,Spin transition ,General Chemistry ,Condensed Matter Physics ,Crystal ,chemistry.chemical_compound ,Crystallography ,chemistry ,Mössbauer spectroscopy ,Pyridine ,General Materials Science ,Single crystal ,Spin-½ - Abstract
Single crystal X-ray diffraction, magnetic and 57Fe Mossbauer spectroscopic studies of a new iron(II)-based spin transition complex – [Fe(3-bpp)2](CF3COO)2 (bpp = 2,6-bis(pyrazol-3-yl)pyridine) are reported. The complex exhibits an incomplete thermal high spin (HS) low spin (LS) transition at ∼226 K which is not associated with any crystallographic transition. Only one of the two crystallographic iron(II) sites undergoes the spin transition, while the other HS site remains invariant of temperature down to 10 K. The origin of the incomplete spin transition is understood by analysing the nature of crystal packing below and above the transition temperature with special attention to the degree of distortion. The present study shows the role of the degree of distortion associated with the cations in the [Fe(3-bpp)2]2+ spin transition complexes.
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- 2021
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9. Chiral metal down to 4.2 K - a BDH-TTP radical-cation salt with spiroboronate anion B(2-chloromandelate)2−
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Hiroshi Nishimoto, Yasuhiro Nakazawa, Michael Brannan, Tomofumi Kadoya, Lee Martin, Hiroki Akutsu, Toby J. Blundell, and Jun-ichi Yamada
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chemistry.chemical_classification ,Chiral ligand ,Metals and Alloys ,Salt (chemistry) ,General Chemistry ,Crystal structure ,Catalysis ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Metal ,Crystallography ,chemistry ,Radical ion ,visual_art ,Materials Chemistry ,Ceramics and Composites ,visual_art.visual_art_medium ,Racemic mixture ,Enantiomer ,Chirality (chemistry) - Abstract
We report the first example of a chiral BDH-TTP radical-cation salt. Chirality is induced in the structure via the use of a chiral spiroboronate anion where three stereocentres are present, one on each chiral ligand and one on the boron centre. Despite starting from a labile racemic mixture of BS and BR enantiomers, only one enantiomer is present in the crystal lattice. The anions pack in a novel double anion layer which is the thickest anion layer found in a BDH-TTP salt. This material is chiral and shows metallic behaviour down to at least 4.2 K.
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- 2021
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10. Systematic study on thermal conductivity of organic triangular lattice systems β′-X[Pd(dmit)2]2
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Tetsuya Nomoto, Satoshi Yamashita, Hiroki Akutsu, Yasuhiro Nakazawa, and Reizo Kato
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- 2022
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11. Molecular conductors from bis(ethylenedithio)tetrathiafulvalene with tris(oxalato)gallate and tris(oxalato)iridate
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Toby J. Blundell, Alexander L. Morritt, Elizabeth K. Rusbridge, Luke Quibell, Jakob Oakes, Hiroki Akutsu, Yasuhiro Nakazawa, Shusaku Imajo, Tomofumi Kadoya, Jun-ichi Yamada, Simon J. Coles, Jeppe Christensen, and Lee Martin
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Chemistry (miscellaneous) ,General Materials Science - Abstract
We present the synthesis, crystal structures and conducting properties of six new BEDT-TTF radical-cation salts with the tris(oxalato)gallate or -iridate anion. The use of halobenzenes gives 4 : 1 β′′ metallic or superconducting salts with tris(oxalato)gallate - fluorobenzene (PhF) or chlorobenzene (PhCl) as a guest molecule gives a metal, whilst the larger bromobenzene (PhBr) or iodobenzene (PhI) gives a superconductor. A 4 : 1 pseudo-κ semiconducting salt is obtained with benzonitrile as the guest molecule for tris(oxalato)iridate, and a novel 5 : 1 metal-insulator phase with tris(oxalato)iridate is also reported.
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- 2022
12. Structure and Properties of a New Purely Organic Magnetic Conductor, δ′-(BEDT-TTF)2(PO-CONHCH(cyclopropyl)SO3)·1.7H2O
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Akiko Kohno, Scott S. Turner, Yasuhiro Nakazawa, and Hiroki Akutsu
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chemistry.chemical_classification ,chemistry.chemical_compound ,Crystallography ,chemistry ,010405 organic chemistry ,Salt (chemistry) ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Tetrathiafulvalene ,0104 chemical sciences ,Ion ,Conductor - Abstract
A new bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF)-based salt with an organic magnetic anion, PO-CONHCH(cyclopropyl)SO3−, has been prepared (PO = 2,2,5,5-tetramethyl-3-pyrrolin-1-oxyl free radi...
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- 2020
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13. Different electronic states of isomorphous chiral vs. racemic organic conducting salts, β′′-(BEDT-TTF)2(S- and rac-PROXYL-CONHCH2SO3)
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Satoshi Yamashita, Akiko Kohno, Scott S. Turner, Hiroki Akutsu, and Yasuhiro Nakazawa
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Materials science ,Point reflection ,02 engineering and technology ,Orders of magnitude (numbers) ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Electronic states ,Metal ,Crystallography ,Chemistry (miscellaneous) ,Electrical resistivity and conductivity ,visual_art ,Atom ,visual_art.visual_art_medium ,General Materials Science ,0210 nano-technology ,Electronic band structure - Abstract
The chiral and racemic salts β′′-(BEDT-TTF)2(S- and rac-PROXYL-CONHCH2SO3) (S-2 and rac-2) are almost isomorphous apart from a deviation in the C–H bond direction at the chiral centre. Both salts are metallic at room temperature, with similar broad metal-insulator transitions. Band structure calculations of the chiral and racemic salts indicate that both electronic structures are quite similar. However, at 30 K, S-2 has a resistivity that is nearly three orders of magnitude higher than that of rac-2. The results suggest a significant effect of the broken inversion symmetry, due to the positional change of only one atom.
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- 2020
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14. Chiral molecular conductor with an insulator–metal transition close to room temperature
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Hiroki Akutsu, Jonathan I Short, Songjie Yang, Toby J. Blundell, Yasuhiro Nakazawa, Lee Martin, John D. Wallis, and Sara J. Krivickas
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Materials science ,Condensed matter physics ,Metals and Alloys ,Insulator (electricity) ,General Chemistry ,Conductivity ,Catalysis ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Conductor ,Metal ,visual_art ,Materials Chemistry ,Ceramics and Composites ,visual_art.visual_art_medium ,Chirality (chemistry) - Abstract
Materials exhibiting both chirality and conductivity do not exist in nature and very few examples have been synthesised. We report here the synthesis of a chiral molecular metal which remains metallic down to at least 4.2 K. This material also exhibits room-temperature switching capabilities with a transition upon cooling below 10 °C.
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- 2020
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15. Enhancements of Superconductivity and Insulating Electrical Resistivity under the Same Uniaxial Strain in a Molecular Conductor
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Yuichi Okii, Takashi Yamamoto, Toshio Naito, Kensuke Konishi, Hiroki Akutsu, and Yasuhiro Nakazawa
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General Physics and Astronomy - Published
- 2022
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16. Enantiopure and racemic radical-cation salts of B(mandelate)
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Toby J, Blundell, Jordan R, Lopez, Kathryn, Sneade, John D, Wallis, Hiroki, Akutsu, Yasuhiro, Nakazawa, Simon J, Coles, Claire, Wilson, and Lee, Martin
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We report the first examples of radical-cation salts of BEDT-TTF with spiroborate anions [B(mandelate)
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- 2022
17. Enantiopure and racemic radical-cation salts of B(mandelate)2− and B(2-chloromandelate)2− anions with BEDT-TTF
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Toby J. Blundell, Jordan R. Lopez, Kathryn Sneade, John D. Wallis, Hiroki Akutsu, Yasuhiro Nakazawa, Simon J. Coles, Claire Wilson, and Lee Martin
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Inorganic Chemistry - Abstract
We report the first examples of radical-cation salts of BEDT-TTF with spiroborate anions [B(mandelate)2]− and [B(2-chloromandelate)2]−, synthesized from either enantiopure or racemic bidentate mandelate or chloromandelate ligands. In the salts prepared using enantiopure ligands only one of two diastereoisomers of the spiroborate anion is incorporated, with the boron centre having the same stereochemistry as the enantiopure ligand. For the racemic salts one racemic pair of spiroborate anions containing an R and an S mandelate ligand is incorporated. In certain solvents helical crystals were obtained when using spiroborate anions with enantiopure ligands. Electrical and magnetic properties, and band structure calculations are reported.
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- 2022
18. Correlation-driven organic 3D topological insulator with relativistic fermions
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Tetsuya Nomoto, Shusaku Imajo, Hiroki Akutsu, Yasuhiro Nakazawa, and Yoshimitsu Kohama
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Condensed Matter - Strongly Correlated Electrons ,Multidisciplinary ,Strongly Correlated Electrons (cond-mat.str-el) ,General Physics and Astronomy ,FOS: Physical sciences ,General Chemistry ,General Biochemistry, Genetics and Molecular Biology - Abstract
Exploring new topological phenomena and functionalities induced by strong electron correlation has been a central issue in modern condensed-matter physics. One example is a topological insulator (TI) state and its functionality driven by the Coulomb repulsion rather than a spin-orbit coupling. Here, we report a "correlation-driven" TI state realized in an organic zero-gap system $\alpha$-(BETS)$_2$I$_3$. The surface metallic state that emerges at low temperatures exhibits characteristic transport properties of a gapless Dirac semimetal, evidencing the presence of a topological surface state in this compound. Moreover, we observe a topological phase switching between the TI state and non-equilibrium Dirac semimetal state by a dc current, which is a unique functionality of a correlation-driven TI state. Our findings demonstrate that correlation-driven TIs are promising candidates not only for practical electronic devices but also as a field for discovering new topological phenomena and phases., Comment: 36 pages including 10 figures
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- 2022
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19. Electronic Heat Capacity and Lattice Softening of Partially Deuterated Compounds of κ-(BEDT-TTF)2Cu[N(CN)2]Br
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Yuki Matsumura, Shusaku Imajo, Satoshi Yamashita, Hiroki Akutsu, and Yasuhiro Nakazawa
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Inorganic Chemistry ,heat capacity ,Crystallography ,strong electron correlations ,Mott transition ,QD901-999 ,General Chemical Engineering ,organic superconductor ,General Materials Science ,Condensed Matter Physics - Abstract
Thermodynamic investigation by calorimetric measurements of the layered organic superconductors, κ-(BEDT-TTF)2Cu[N(CN)2]Br and its partially deuterated compounds of κ-(d[2,2]-BEDT-TTF)2Cu[N(CN)2]Br and κ-(d[3,3]-BEDT-TTF)2Cu[N(CN)2]Br, performed in a wide temperature range is reported. The latter two compounds were located near the metal–insulator boundary in the dimer-Mott phase diagram. From the comparison of the temperature dependences of their heat capacities, we indicated that lattice heat capacities of the partially deuterated compounds were larger than that of the pristine compound below about 40 K. This feature probably related to the lattice softening was discussed also by the sound velocity measurement, in which the dip-like structures of the Δv/v were observed. We also discussed the variation of the electronic heat capacity under magnetic fields. From the heat capacity data at magnetic fields up to 6 T, we evaluated that the normal-state γ value of the partially deuterated compound, κ-(d[3,3]-BEDT-TTF)2Cu[N(CN)2]Br, was about 3.1 mJ K−2 mol−1. Under the magnetic fields higher than 3.0 T, we observed that the magnetic-field insulating state was induced due to the instability of the mid-gap electronic state peculiar for the two-dimensional dimer-Mott system. Even though the volume fraction was much reduced, the heat capacity of κ-(d[3,3]-BEDT-TTF)2Cu[N(CN)2]Br showed a small hump structure probably related to the strong coupling feature of the superconductivity near the boundary.
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- 2021
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20. Fermi Surface Structure and Isotropic Stability of Fulde-Ferrell-Larkin-Ovchinnikov Phase in Layered Organic Superconductor β″-(BEDT-TTF)2SF5CH2CF2SO3
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Shiori Sugiura, Hiroki Akutsu, Yasuhiro Nakazawa, Taichi Terashima, Syuma Yasuzuka, John A. Schlueter, and Shinya Uji
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Condensed Matter::Quantum Gases ,Crystallography ,General Chemical Engineering ,FFLO phase ,MathematicsofComputing_GENERAL ,organic superconductor ,Condensed Matter Physics ,vortex dynamics ,Inorganic Chemistry ,resistance ,TheoryofComputation_MATHEMATICALLOGICANDFORMALLANGUAGES ,QD901-999 ,Condensed Matter::Superconductivity ,Condensed Matter::Strongly Correlated Electrons ,General Materials Science - Abstract
The Fermi surface structure of a layered organic superconductor β″-(BEDT-TTF)2SF5CH2CF2SO3 was determined by angular-dependent magnetoresistance oscillations measurements and band-structure calculations. This salt was found to have two small pockets with the same area: a deformed square hole pocket and an elliptic electron pocket. Characteristic corrugations in the field dependence of the interlayer resistance in the superconducting phase were observed at any in-plane field directions. The features were ascribed to the commensurability (CM) effect between the Josephson vortex lattice and the periodic nodal structure of the superconducting gap in the Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) phase. The CM effect was observed in a similar field region for various in-plane field directions, in spite of the anisotropic nature of the Fermi surface. The results clearly showed that the FFLO phase stability is insensitive to the in-plane field directions.
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- 2021
21. Perspectives on Molecular Materials—A Tribute to Professor Peter Day
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Scott S. Turner, Lee Martin, Carlos J. Gómez-García, Hiroki Akutsu, and John D. Wallis
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Chemistry ,n/a ,Chemistry (miscellaneous) ,media_common.quotation_subject ,Materials Chemistry ,Tribute ,Grammar school ,Art ,Molecular materials ,QD1-999 ,Classics ,Electronic, Optical and Magnetic Materials ,media_common - Abstract
Professor Peter Day FRS was born on 20 August 1938 in Kent (UK) and attended Maidstone Grammar School [...]
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- 2021
22. Exceptionally high temperature spin crossover in amide-functionalised 2,6-bis(pyrazol-1-yl)pyridine iron(ii) complex revealed by variable temperature Raman spectroscopy and single crystal X-ray diffraction
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Pierre Le Maguere, Max Attwood, Lee Martin, Scott S. Turner, Hiroki Akutsu, and Toby J. Blundell
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Inorganic Chemistry ,symbols.namesake ,Crystallography ,Materials science ,Differential scanning calorimetry ,Spin states ,Hydrogen bond ,Spin crossover ,X-ray crystallography ,symbols ,Crystal structure ,Raman spectroscopy ,Single crystal - Abstract
The synthesis of a novel amide-functionalised 2,6-bis(pyrazol-1-yl)pyridine-4-carboxamide ligand (bppCONH2) is described. The complex salts [Fe(bppCONH2)2](BF4)2 and [Fe(bppCONH2)2](ClO4)2 were synthesised and characterised by SQUID magnetometry, differential scanning calorimetry, variable temperature Raman spectroscopy and single crystal X-ray diffraction. DSC measurements of [Fe(bppCONH2)2](BF4)2 indicate a spin-crossover (SCO) transition with T↑ at 481 K and T↓ at 461 K, showing a 20 K hysteresis. DSC for the perchlorate salt shows an SCO transition with T↑ at 459 K and T↓ at 445 K with a 14 K hysteresis. For the BF4− salt analysis of low and high-spin state crystal structures at 101, 290 and 500 K, suggest stabilisation of the low spin state due to the formation of 1D hydrogen-bonded cationic chains. Variable temperature Raman studies of the BF4 salt support the presence of a high temperature SCO. It is speculated that the presence of hysteresis may be attributed to differences in the inter-molecular hydrogen bonding in the low spin and high spin states.
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- 2021
23. Structures and Properties of New Organic Molecule-Based Metals, (D)2BrC2H4SO3 [D = BEDT-TTF and BETS]
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Hiroki Akutsu, Yuta Koyama, Yasuhiro Nakazawa, and Scott S. Turner
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crystal structure ,Materials science ,band structure ,Crystal structure ,organic anions ,Metal ,organic conductors ,chemistry.chemical_compound ,Electrical resistivity and conductivity ,Materials Chemistry ,Molecule ,electrocrystallization ,Electronic band structure ,QD1-999 ,biology ,Magnetic susceptibility ,Electronic, Optical and Magnetic Materials ,Chemistry ,Crystallography ,chemistry ,Chemistry (miscellaneous) ,visual_art ,visual_art.visual_art_medium ,biology.protein ,electrical resistivity ,magnetic susceptibility ,Tetrathiafulvalene ,Organic anion - Abstract
An organic anion, 2-bromoethanesulfonate (BrC2H4SO3−), provides one bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) and two bis(ethylenedithio)tetraselenafulvalene (BETS) salts, the compositions of which are β’’-β’’-(BEDT-TTF)2BrC2H4SO3 (1), β’’-β’’-(BETS)2BrC2H4SO3 (2), and θ-(BETS)2BrC2H4SO3 (3), respectively. Compound 1 shows a metal–insulator transition at around 70 K. Compound 2 is isomorphous to 1, and 3 is polymorphic with 2. Compounds 2 and 3 show metallic behavior at least down to 4.2 K. The pressure dependence of the electrical resistivity of 1 is also reported.
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- 2021
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24. First Molecular Superconductor with the Tris(Oxalato)Aluminate Anion, β″-(BEDT-TTF)4(H3O)Al(C2O4)3·C6H5Br, and Isostructural Tris(Oxalato)Cobaltate and Tris(Oxalato)Ruthenate Radical Cation Salts
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Yasuhiro Nakazawa, Shusaku Imajo, Toby J. Blundell, Hiroki Akutsu, Michael Brannan, Lee Martin, and Joey Mburu-Newman
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Tris ,Chemistry ,Aluminate ,Metal ions in aqueous solution ,02 engineering and technology ,Crystal structure ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,Paramagnetism ,Crystallography ,chemistry.chemical_compound ,Metallate ,Radical ion ,Chemistry (miscellaneous) ,Materials Chemistry ,Isostructural ,0210 nano-technology ,molecular conductor ,superconductor ,metal ,semiconductor ,BEDT-TTF ,tris(oxalato)metallate - Abstract
Peter Day’s research group reported the first molecular superconductor containing paramagnetic metal ions in 1995, β″-(BEDT-TTF)4(H3O)Fe(C2O4)3·C6H5CN. Subsequent research has produced a multitude of BEDT-TTF-tris(oxalato)metallate salts with a variety of structures and properties, including 32 superconductors to date. We present here the synthesis, crystal structure, and conducting properties of the newest additions to the Day series including the first superconductor incorporating the diamagnetic tris(oxalato)aluminate anion, β″-(BEDT-TTF)4(H3O)Al(C2O4)3·C6H5Br, which has a superconducting Tc of ~2.5 K. β″-(BEDT-TTF)4(H3O)Co(C2O4)3·C6H5Br represents the first example of a β″ phase for the tris(oxalato)cobaltate anion, but this salt does not show superconductivity.
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- 2021
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25. Extraordinary $\pi$-Electron Superconductivity Emerging from a Quantum Spin Liquid
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Yoshimitsu Kohama, Taichi Terashima, Hiroki Akutsu, Shusaku Imajo, S. Uji, Shiori Sugiura, Yasuhiro Nakazawa, Takayuki Isono, and K. Kindo
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Superconductivity ,Physics ,Condensed Matter - Materials Science ,Condensed matter physics ,Spins ,Condensed Matter - Superconductivity ,Doping ,Electron ,Condensed Matter - Strongly Correlated Electrons ,Metallic conductivity ,Condensed Matter::Superconductivity ,Hexagonal lattice ,Condensed Matter::Strongly Correlated Electrons ,Quantum spin liquid ,Critical field - Abstract
Quantum spin liquids (QSLs), in which spins are highly entangled, have been considered a groundwork for generating exotic superconductivity. Despite numerous efforts, superconductivity emerging from QSLs has been unrealized in actual materials due to the difficulties in stabilizing QSL states with metallic conductivity. Recently, an organic compound, $\ensuremath{\kappa}\text{\ensuremath{-}}{(\mathrm{BEDT}\text{\ensuremath{-}}\mathrm{TTF})}_{4}{\mathrm{Hg}}_{2.89}{\mathrm{Br}}_{8}$, with a nearly regular triangular lattice of molecular dimers was recognized as a candidate for doped QSLs. In this study, we report an unusual superconducting phase of $\ensuremath{\kappa}\text{\ensuremath{-}}{(\mathrm{BEDT}\text{\ensuremath{-}}\mathrm{TTF})}_{4}{\mathrm{Hg}}_{2.89}{\mathrm{Br}}_{8}$: unexpectedly large ratios of the upper critical field to the critical temperature ${H}_{\mathrm{c}2}/{T}_{\mathrm{c}}$ in fields not only parallel but also perpendicular to the two-dimensional conducting layers and a very wide region of fluctuating superconductivity above ${T}_{\mathrm{c}}$. Our results reveal that these peculiarities arise from strong electron correlations and possible quantum criticality unique to the doped QSL state, leading to a heavy mass of itinerant carriers and a large superconducting energy gap.
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- 2021
26. First Molecular Superconductor with the Tris(Oxalato)Aluminate Anion, β″-(BEDT-TTF)4(H3O)Al(C2O4)3·C6H5Br, and Isostructural Tris(Oxalato)Cobaltate and Tris(Oxalato)Ruthenate Radical Cation Salts
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Toby James Blundell, Michael Brannan, Joey Mburu-Newman, Hiroki Akutsu, Yasuhiro Nakazawa, Shusaku Imajo, and Lee Martin
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tris(oxalato)metallate ,Chemistry ,superconductor ,metal ,semiconductor ,QD1-999 ,BEDT-TTF ,molecular conductor - Abstract
Peter Day’s research group reported the first molecular superconductor containing paramagnetic metal ions in 1995, β″-(BEDT-TTF)4(H3O)Fe(C2O4)3·C6H5CN. Subsequent research has produced a multitude of BEDT-TTF-tris(oxalato)metallate salts with a variety of structures and properties, including 32 superconductors to date. We present here the synthesis, crystal structure, and conducting properties of the newest additions to the Day series including the first superconductor incorporating the diamagnetic tris(oxalato)aluminate anion, β″-(BEDT-TTF)4(H3O)Al(C2O4)3·C6H5Br, which has a superconducting Tc of ~2.5 K. β″-(BEDT-TTF)4(H3O)Co(C2O4)3·C6H5Br represents the first example of a β″ phase for the tris(oxalato)cobaltate anion, but this salt does not show superconductivity.
- Published
- 2021
27. New Spin-Crossover Compounds Containing the [Ni(mnt)] Anion (mnt = Maleonitriledithiolate)
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Peter N. Horton, Scott S. Turner, Hiroki Akutsu, Volker Schünemann, Simon J. Coles, and Joanna Daniell
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Pyrazine ,Chemistry ,Cationic polymerization ,spin-crossover ,molecular magnets ,magnetic materials ,molecular materials ,Electronic, Optical and Magnetic Materials ,Ion ,Magnetization ,chemistry.chemical_compound ,Crystallography ,Chemistry (miscellaneous) ,Spin crossover ,Mössbauer spectroscopy ,Pyridine ,Materials Chemistry ,QD1-999 ,Single crystal - Abstract
Two novel salts containing the anion [Ni(mnt)2]− (mnt = maleonitriledithiolate) have been synthesized. The counter-ions, [Fe(II)(L1 or L2)2], are cationic complexes where L1 and L2 are methylated derivatives of 2,6-bis(pyazolyl)pyridine or pyrazine, which are similar to ligands found in a series of spin-crossover (SCO) complexes. Both salts are characterized by variable temperature single crystal X-ray diffraction and bulk magnetization measurements. Compound 1, [Fe(II)(L1)2][Ni(mnt)2]2 displays an incomplete and gradual SCO up to 300 K, followed by a more rapid increase in the high-spin fraction between 300 and 350 K. Compound 2, [Fe(II)(L2)2][Ni(mnt)2]2.MeNO2, shows a gradual, but more complete SCO response centered at 250 K. For compound 2, the SCO is confirmed by variable temperature Mössbauer spectroscopy. In both cases, the anionic moieties are isolated from each other and so no electrical conductivity is observed.
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- 2021
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28. Chiral metal down to 4.2 K - a BDH-TTP radical-cation salt with spiroboronate anion B(2-chloromandelate)
- Author
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Toby J, Blundell, Michael, Brannan, Hiroshi, Nishimoto, Tomofumi, Kadoya, Jun-Ichi, Yamada, Hiroki, Akutsu, Yasuhiro, Nakazawa, and Lee, Martin
- Abstract
We report the first example of a chiral BDH-TTP radical-cation salt. Chirality is induced in the structure via the use of a chiral spiroboronate anion where three stereocentres are present, one on each chiral ligand and one on the boron centre. Despite starting from a labile racemic mixture of BS and BR enantiomers, only one enantiomer is present in the crystal lattice. The anions pack in a novel double anion layer which is the thickest anion layer found in a BDH-TTP salt. This material is chiral and shows metallic behaviour down to at least 4.2 K.
- Published
- 2021
29. Large-Amplitude Thermal Vibration-Coupled Valence Tautomeric Transition Observed in a Conductive One-Dimensional Rhodium-Dioxolene Complex
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Minoru Mitsumi, Hiroki Akutsu, Koshiro Toriumi, Haruo Akashi, Yasutaka Kitagawa, Masahiro Hashimoto, Yuji Miyazaki, and Yuuki Komatsu
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Phase transition ,Valence (chemistry) ,Chemistry ,Organic Chemistry ,chemistry.chemical_element ,General Chemistry ,Tautomer ,Catalysis ,Rhodium ,Vibration ,Amplitude ,X-ray photoelectron spectroscopy ,Chemical physics ,Thermal ,Physics::Atomic and Molecular Clusters - Abstract
The exploration of dynamic molecular crystals is a fascinating theme for materials scientists owing to their fundamental science and potential application to molecular devices. Herein, a one-dimensional (1D) rhodium-dioxolene complex is reported that exhibits drastic changes in properties with the phase transition. X-ray photoelectron spectroscopy (XPS) revealed that the room-temperature (RT) phase is in a mixed-valence state, and therefore, the drastic changes originate from the mixed-valence state appearing in the RT phase. Another notable feature is that the mean square displacements of the rhodium atoms along the 1D chain dramatically increased in the RT phase, indicating a large-amplitude vibration of the Rh-Rh bonds. From these results, a possible mechanism for the appearance of the mixed-valence state in the RT phase was proposed based on the thermal electron transfer from the 1D d-band to the semiquinonato π* orbital coupled with the large-amplitude vibration of the Rh-Rh bonds.
- Published
- 2020
30. Structures and Properties of New Organic Conductors: BEDT-TTF, BEST and BETS Salts of the HOC2H4SO3− Anion
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Hiroki Akutsu, Yuta Koyama, Keigo Furuta, Scott S. Turner, and Yasuhiro Nakazawa
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Madelung energy ,Materials science ,General Chemical Engineering ,Salt (chemistry) ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Ion ,Inorganic Chemistry ,Metal ,chemistry.chemical_compound ,organic conductors ,Electrical resistivity and conductivity ,bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) ,bis(ethylenedithio)tetraselenafulvalene (BETS) ,lcsh:QD901-999 ,General Materials Science ,Isostructural ,Electrical conductor ,chemistry.chemical_classification ,bis(ethylenediseleno)tetrathiafulvalene (BEST) ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Magnetic susceptibility ,0104 chemical sciences ,Crystallography ,chemistry ,visual_art ,visual_art.visual_art_medium ,quantum chemical calculations ,lcsh:Crystallography ,charge-ordered state ,0210 nano-technology ,Tetrathiafulvalene ,X-ray analysis ,electrical resistivity ,magnetic susceptibility - Abstract
New bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF)-, bis(ethylenediseleno)tetrathiafulvalene (BEST)- and bis(ethylenedithio)tetraselenafulvalene (BETS)-based organic charge-transfer (CT) salts&mdash, &alpha, (BEDT-TTF)3(HOC2H4SO3)2 (1), &beta, (BEST)3(HOC2H4SO3)2·, H2O (2) and &alpha, (BETS)2(HOC2H4SO3)·, H2O (3)&mdash, have been prepared. Salts 1 and 2 show semiconducting behaviour. Salt 3, which is almost isostructural to &alpha, (BETS)2I3, shows metallic behaviour down to 70 K and then shows a broader metal&ndash, insulator transition than that of &alpha, (BETS)2I3. The reason for the difference in behaviour is estimated by the comparison of the Madelung energies of the full set of patterns of possible donor&rsquo, s charge-ordered and anion&rsquo, s disordered states.
- Published
- 2020
31. Anisotropic Fully-Gapped Superconductivity Possibly Mediated by Charge Fluctuations in a Nondimeric Organic Complex
- Author
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Masashi Tokunaga, Hiroki Akutsu, K. Kindo, Takeshi Yajima, Shusaku Imajo, Yoshimitsu Kohama, Yasuhiro Nakazawa, and Ryosuke Kurihara
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Superconductivity ,Physics ,Condensed matter physics ,Strongly Correlated Electrons (cond-mat.str-el) ,Condensed Matter - Superconductivity ,General Physics and Astronomy ,Quantum oscillations ,FOS: Physical sciences ,Charge (physics) ,Fermi surface ,01 natural sciences ,Heat capacity ,Superconductivity (cond-mat.supr-con) ,Condensed Matter - Strongly Correlated Electrons ,Pairing ,Condensed Matter::Superconductivity ,0103 physical sciences ,Organic superconductor ,010306 general physics ,Anisotropy - Abstract
We investigate low-temperature electronic properties of the nondimeric organic superconductor $\beta^{\prime\prime}$-(BEDT-TTF)$_4$[(H$_3$O)Ga(C$_2$O$_4$)$_3$]PhNO$_2$. By examining ultrasonic properties, charge disproportionation (CD) without magnetic field dependence is detected below $T_{\rm CD}$$\sim$8~K just above the superconducting critical temperature $T_{\rm c}$$\sim$6~K. From quantum oscillations in high fields, we find variation in the Fermi surface and mass enhancement induced by the CD. Heat capacity studies elucidate that the superconducting gap function is fully gapped in the Fermi surface, but anisotropic with fourfold symmetry. We point out that the pairing mechanism of the superconductivity is possibly dominated by charge fluctuations., Comment: 6 figures
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- 2020
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32. Construction of a thermal conductivity measurement system for small single crystals of organic conductors
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Satoshi Yamashita, Yasuhiro Nakazawa, Tetsuya Nomoto, Hiroki Akutsu, Alexander I. Krivchikov, and Shusaku Imajo
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Phase transition ,Materials science ,Drop (liquid) ,Analytical chemistry ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,010406 physical chemistry ,0104 chemical sciences ,Thermal conductivity measurement ,chemistry.chemical_compound ,Thermal conductivity ,chemistry ,Molecule ,Physical and Theoretical Chemistry ,0210 nano-technology ,Electrical conductor ,Tetrathiafulvalene - Abstract
We newly constructed a thermal conductivity measurement system for single crystals of molecular compounds. This system enables us to measure the thermal conductivity of samples with the length of less than 1.0 mm. In order to evaluate the capability of detection of phase transitions occurred in molecule-based materials, we performed the thermal conductivity measurement of single crystals of organic conductors α-(BEDT-TTF)2I3 and κ-(BEDT-TTF)2Cu[N(CN)2]Br, where BEDT-TTF denotes bis(ethylenedithio)tetrathiafulvalene. From the temperature dependence of the thermal conductivity of α-(BEDT-TTF)2I3, we succeeded in observing the metal–insulator transition as a sudden drop of κ(T) at 135 K. In the temperature dependence of thermal conductivity of κ-(BEDT-TTF)2Cu[N(CN)2]Br, we could observe the increment of κ(T) at the metal-superconducting transition (Tc = 11.4 K). These results show that the newly developed system has high performance enough to detect various kinds of phase transitions in small crystals of molecular compounds.
- Published
- 2018
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33. A new Ni(dmit)2-based organic magnetic charge-transfer salt, (m-PO-CONH-N-methylpyridinium)[Ni(dmit)2]·CH3CN
- Author
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Soichi Ito, Tomofumi Kadoya, Shin'ichi Nakatsuji, Jun-ichi Yamada, Hiroki Akutsu, Scott S. Turner, and Yasuhiro Nakazawa
- Subjects
chemistry.chemical_classification ,Spins ,010405 organic chemistry ,Radical ,Salt (chemistry) ,Crystal structure ,010402 general chemistry ,01 natural sciences ,Magnetic susceptibility ,0104 chemical sciences ,Inorganic Chemistry ,Crystallography ,chemistry ,Ferromagnetism ,Mean field theory ,Materials Chemistry ,Physical and Theoretical Chemistry ,Spin (physics) - Abstract
A new Ni(dmit)2-based organic magnetic charge-transfer (CT) salt, (m-PO-CONH-N-methylpyridinium)[Ni(dmit)2]·CH3CN, where PO = 2,2,5,5-Tetramethyl-3-pyrrolin-1-oxyl free radical and dmit = 2-Thioxo-1,3-dithiole-4,5-dithiolate, was obtained, the crystal structure and magnetic properties of which are reported. Magnetic susceptibility of the CT salt obeys a combination of 1D ferromagnetic (1DF) Heisenberg (J1DF = +0.26 K) and Singlet-Triplet (ST) models (JST = -51.2 K) with mean field (MF) approximation (JMF = -6.7 K), suggesting that spins on the PO radicals form 1D ferromagnetic chains and spins on the Ni(dmit)2 monoanions forms spin dimers at low temperature, the latter of which was also confirmed by band calculations.
- Published
- 2018
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34. Bulk Kosterlitz–Thouless Type Molecular Superconductor β″-(BEDT-TTF)2[(H2O)(NH4)2Cr(C2O4)3]·18-crown-6
- Author
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Jordan R. Lopez, Lee Martin, Shusaku Imajo, Hiroki Akutsu, and Yasuhiro Nakazawa
- Subjects
Superconductivity ,Superstructure ,18-Crown-6 ,02 engineering and technology ,Crystal structure ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Magnetic field ,Ion ,Inorganic Chemistry ,chemistry.chemical_compound ,Crystallography ,chemistry ,Molecule ,Physical and Theoretical Chemistry ,0210 nano-technology ,Critical field - Abstract
A new molecular superconductor, β”-(BEDTTTF)2[(H2O)(NH4)2Cr(C2O4)3].18-crown-6, has been synthesized from the organic donor molecule BEDT-TTF with the anion Cr(C2O4)3 3- . The crystal structure consists of conducting organic layers of BEDT-TTF molecules which adopt the β” packing motif (layer A), layers of NH4 + and Λ-Cr(C2O4)3 3- (layer B), layers of (H2O)(NH4)18- crown-6 (layer C), and layers of NH4 + and Δ-Cr(C2O4)3 3- (layer D) which produce a superstructure with a repeating pattern of ABCDABCDA. As a result of this packing arrangement this is the 2D superconductor with the widest gap between conducting layers where only a single donor packing motif is present (β”). Superconducting critical temperatures at ambient pressure observed by electrical transport and magnetic measurements are 4.0- 4.9 and 2.5 K, respectively. The strong 2D nature of this system, the broad transition to Tzero at 1.8K, and the transition of α of V ∝ Iα from 1 to 3 on I-V curves strongly suggests that the superconducting transition is very close to a Kosterlitz-Thouless transition. The magnetic field dependence of the superconducting critical temperature parallel to the conducting plane gives an upper critical field μ0Hc2// > 8 T, which is over the calculated Pauli-Clogston limit for this material.
- Published
- 2017
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35. Anion polarity-induced self-doping in a purely organic paramagnetic conductor, α′-α′-(BEDT-TTF) 2 (PO-CONH- m -C 6 H 4 SO 3 )·H 2 O where BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene and PO is the radical 2,2,5,5-Tetramethyl-3-pyrrolin-1-oxyl
- Author
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Shin'ichi Nakatsuji, Soich Ito, Scott S. Turner, Yasuhiro Nakazawa, Keita Ishihara, Jun-ichi Yamada, Hiroki Akutsu, and Fumiyoshi Nishiyama
- Subjects
Stereochemistry ,Doping ,Fermi level ,02 engineering and technology ,Crystal structure ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Magnetic susceptibility ,0104 chemical sciences ,Ion ,Inorganic Chemistry ,Dipole ,Paramagnetism ,chemistry.chemical_compound ,Crystallography ,symbols.namesake ,chemistry ,Materials Chemistry ,symbols ,Physical and Theoretical Chemistry ,0210 nano-technology ,Tetrathiafulvalene - Abstract
A new BEDT-TTF-based salt with an organic free radical, α′-α′-(BEDT-TTF)2(PO-CONH-m-C6H4SO3)·H2O, has been prepared. The crystal structure consists of alternating donor and anion/water layers propagated along the c axis. The anisotropic radical anions form a head-to-head arrangement, which provides a permanent dipole moment. The effect on the nearest donor layer has been estimated to be 4.0 V. The salt has two crystallographically independent donor layers (A and B), one of which (A) is surrounded by the negative ends of the anion layer dipole whereas the B layers are bordered by the positive ends of the dipole. This structural feature suggests that layers A and B have different Fermi levels. To eliminate the imbalance, self-doping occurs whereby electron density is transferred from layer A to B. The temperature dependence of the magnetic susceptibility has 11.1% of extra Curie spins, from which a doping ratio of 12.7% has been estimated.
- Published
- 2017
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36. Increase in the Magnetic Ordering Temperature (Tc) as a Function of the Applied Pressure for A2Mn[Mn(CN)6] (A = K, Rb, Cs) Prussian Blue Analogues
- Author
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M. Sugimoto, Christopher M. Kareis, Jack G. DaSilva, Shinsuke Yamashita, Hiroki Akutsu, Joel S. Miller, and Yasuhiro Nakazawa
- Subjects
Prussian blue ,Chemistry ,Transition temperature ,Hydrostatic pressure ,Analytical chemistry ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,Magnetization ,chemistry.chemical_compound ,Nuclear magnetic resonance ,Ferrimagnetism ,Physical and Theoretical Chemistry ,0210 nano-technology ,Néel temperature ,Ambient pressure ,Monoclinic crystal system - Abstract
Magnetization measurements under pressure reveal that the external hydrostatic pressure significantly increases in the ferrimagnetic transition temperature, Tc, for A2Mn[Mn(CN)6] (A = K, Rb, Cs). In the case of monoclinic A = K and Rb, dTc/dp values are 21.2 and 14.6 K GPa–1, respectively, and Tc increases by 53 and 39%, respectively, from ambient pressure to 1.0 GPa. The cubic A = Cs compound also shows a monotonous increase with an initial rate of 4.22 K GPa–1 and about 11.4 K GPa–1 above 0.6 GPa, and an overall Tc increase by 26% at 1.0 GPa. The increase in Tc is attributed to deformation of the structure such that the MnII—N≡C angle decreases with increasing pressure. The smaller the alkali cation, the greater the decrease in the MnII—N≡C angle induced by pressure and the larger the increase of dTc/dp. This is in accordance with the ambient-pressure structures for A2Mn[Mn(CN)6] (A = K, Rb, Cs), which have decreasing MnII—N≡C angles that correlate to the observed increasing Tcs as K > Rb > Cs. The larg...
- Published
- 2017
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37. Enantiopure and racemic radical-cation salts of bis(2′-hydroxylpropylthio)(ethylenedithio)TTF with polyiodide anions
- Author
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Anthony Christian, Shin'ichi Nakatsuji, Milena A. Guziak, Hiroki Akutsu, Peter Maksymiw, Lee Martin, John D. Wallis, Jun-ichi Yamada, and Florence Konalian-Kempf
- Subjects
Stereochemistry ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,chemistry.chemical_compound ,Polyiodide ,Crystallography ,Enantiopure drug ,chemistry ,Radical ion ,Side chain ,Molecule ,Triiodide ,Enantiomer ,0210 nano-technology ,Tetrathiafulvalene - Abstract
The chiral TTF-based donor molecule bis(2′-hydroxylpropylthio)(ethylenedithio)tetrathiafulvalene (BHPT-EDT-TTF) has produced enantiopure R,R and S,S radical-cation salts with polyiodide anions I3− and I82−. Enantiomorphic 6 : 6 donor : I3 phases grown from either the R,R or S,S donor are semiconducting with similar activation energies of 0.24–0.30 eV and 0.22–0.23 eV, respectively, and contain three unique face-to-face donor pairs whose relative orientation is determined by side chain conformations and hydrogen bonding. Racemic material under the same conditions gave an insulating centrosymmetric phase with R,R and S,S donor cations in a face-to-face pair partnered with an octaiodide dianion, and with a ca. 3 : 1 disorder between the enantiomers. Enantiopure BHPT-EDT-TTF yielded two further insulating crystalline phases of composition 2 : 2 with triiodide and 2 : 1 with octaiodide.
- Published
- 2017
- Full Text
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38. Multilayer Coated Microstructure for Solar Selective Absorbers
- Author
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Hiroo Yugami, Hiroki Akutsu, Masafumi Kumano, Makoto Shimizu, Shinichiro Tsuda, and Kosuke Hikichi
- Subjects
010302 applied physics ,Materials science ,Mechanical Engineering ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,Atomic layer deposition ,Thermal radiation ,0103 physical sciences ,Electrical and Electronic Engineering ,Composite material ,0210 nano-technology ,Periodic microstructure - Published
- 2017
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39. Effects of electron correlations and chemical pressures on superconductivity of β′′ -type organic compounds
- Author
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Alexander L. Morritt, A Akutsu-Sato, Yasuhiro Nakazawa, Hiroki Akutsu, Shusaku Imajo, and Lee Martin
- Subjects
Superconductivity ,chemistry.chemical_compound ,Materials science ,Effective mass (solid-state physics) ,Electrical resistance and conductance ,chemistry ,Chemical physics ,Pairing ,Condensed Matter::Strongly Correlated Electrons ,Disproportionation ,Electron ,Tetrathiafulvalene ,Magnetic field - Abstract
We investigate low-temperature electronic states of the series of organic conductors β'' - [bis(ethylenedithio)tetrathiafulvalene] 4[(H3O)M(C2O4)3] G, where M and G represent trivalent metalions and guest organic molecules, respectively. Our structural analyses reveal that the replacement of M and G give rise to systematic change in the cell parameters, especially in the b-axis length, which has a positive correlation with the superconducting transition temperature Tc. Analysis of temperature and magnetic field dependences of the electrical resistance including the Shubnikov–de Haas oscillations elucidates that the variation of charge disproportionation, the effective mass, and the number of itinerant carriers can be systematically explained by the change of the b-axis length. The changes of the transfer integrals induced by stretching/compressing the b axis are confirmed by the band calculation. We discuss that electron correlations in quarter-filled electronic bands lead to charge disproportionation and the possibility of a novel pairing mechanism of superconductivity mediated by charge degrees of freedom.
- Published
- 2019
- Full Text
- View/download PDF
40. Above room temperature spin crossover in thioamide-functionalised 2,6-bis(pyrazol-1-yl)pyridine iron(ii) complexes
- Author
-
Max Attwood, Scott S. Turner, Hiroki Akutsu, Lee Martin, and Dyanne L. Cruickshank
- Subjects
Inorganic Chemistry ,chemistry.chemical_classification ,chemistry.chemical_compound ,Crystallography ,Differential scanning calorimetry ,chemistry ,Spin states ,Spin crossover ,Pyridine ,Cooperativity ,Crystal structure ,Single crystal ,Thioamide - Abstract
This work describes the synthesis of two novel functionalised 2,6-bis(pyrazol-1-yl)pyridine (bpp) ligands, namely 2,6-bis(pyrazol-1-yl)pyridine-4-carbothioamide (bppCSNH2) and N-methyl-2,6-bis(pyrazol-1-yl)pyridine-4-carbothioamide (bppCSNHMe). The corresponding solvated or non-solvated Fe(II) salts, [Fe(bppCSNH2)2]X2 and [Fe(bppCSNHMe)2]X2 (X = BF4− or ClO4−) were synthesised and their properties measured by SQUID magnetometry, Evans NMR, differential scanning calorimetry and single crystal X-ray diffraction. In the solid state [Fe(bppCSNH2)2]2+ salts persist in the low spin state below 350 K. The structure of [Fe(bppCSNH2)2](BF4)2·2MeNO2 shows a network of intermolecular interactions responsible for the low spin state stabilisation, relative to the prototypical [Fe(bpp)2]2+ spin crossover (SCO) salts. By contrast the complexes of bppCSNHMe both display abrupt SCO above 300 K. [Fe(bppCSNHMe)2](BF4)2·MeNO2 requires solvent loss before SCO can be observed centred at 332 K. The non-solvated [Fe(bppCSNHMe)2](ClO4)2 shows SCO centred at 325 K. Analysis of solvated and non-solvated crystal structures suggests that cooperativity is facilitated by thioamide-group interactions with neighbouring pyrazolyl and pyridyl moieties.
- Published
- 2019
41. 2D Molecular Superconductor to Insulator Transition in the β'-(BEDT-TTF)
- Author
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Alexander L, Morritt, Jordan R, Lopez, Toby J, Blundell, Enric, Canadell, Hiroki, Akutsu, Yasuhiro, Nakazawa, Shusaku, Imajo, and Lee, Martin
- Abstract
The series of salts β''-(BEDT-TTF)
- Published
- 2019
42. Magnetic and Electronic Properties of π-d Interacting Molecular Magnetic Superconductor κ-(BETS)2FeX4 (X = Cl, Br) Studied by Angle-Resolved Heat Capacity Measurements
- Author
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Hiroki Akutsu, Shuhei Fukuoka, Sotarou Fukuchi, Yasuhiro Nakazawa, and Atsushi Kawamoto
- Subjects
Materials science ,General Chemical Engineering ,magnetic conductor ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Heat capacity ,Inorganic Chemistry ,single crystal heat capacity measurement ,lcsh:QD901-999 ,Antiferromagnetism ,General Materials Science ,Anisotropy ,Superconductivity ,thermodynamic measurement ,Condensed matter physics ,Transition temperature ,superconductivity ,π-d system ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,0104 chemical sciences ,Magnetic field ,Magnetic anisotropy ,Magnet ,antiferromagnetism ,lcsh:Crystallography ,0210 nano-technology - Abstract
Thermodynamic picture induced by π-d interaction in a molecular magnetic superconductor κ-(BETS)2FeX4 (X = Cl, Br), where BETS is bis(ethylenedithio)tetraselenafulvalene, studied by single crystal calorimetry is reviewed. Although the S = 5/2 spins of Fe3+ in the anion layers form a three-dimensional long-range ordering with nearly full entropy of Rln6, a broad hump structure appears in the temperature dependence of the magnetic heat capacity only when the magnetic field is applied parallel to the a axis, which is considered as the magnetic easy axis. The scaling of the temperature dependence of the magnetic heat capacity of the two salts is possible using the parameter of |Jdd|/kB and therefore the origin of the hump structure is related to the direct magnetic interaction, Jdd, that is dominant in the system. Quite unusual crossover from a three-dimensional ordering to a one-dimensional magnet occurs when magnetic fields are applied parallel to the a axis. A notable anisotropic field-direction dependence against the in-plane magnetic field was also observed in the transition temperature of the bulk superconductivity by the angle-resolved heat capacity measurements. We discuss the origin of this in-plane anisotropy in terms of the 3d electron spin configuration change induced by magnetic fields.
- Published
- 2019
43. 2D Molecular Superconductor to Insulator Transition in the β′′- (BEDT-TTF)2[(H2O)(NH4)2M(C2O4)3]·18-crown‑6 Series (M = Rh, Cr, Ru, Ir)
- Author
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Enric Canadell, Toby J. Blundell, Hiroki Akutsu, Jordan R. Lopez, Lee Martin, Alexander L. Morritt, Yasuhiro Nakazawa, Shusaku Imajo, Japan Society for the Promotion of Science, Royal Society (UK), Ministerio de Ciencia, Innovación y Universidades (España), and Generalitat de Catalunya
- Subjects
Inorganic Chemistry ,Superconductivity ,chemistry.chemical_compound ,Crystallography ,chemistry ,Series (mathematics) ,010405 organic chemistry ,18-Crown-6 ,Physical and Theoretical Chemistry ,Insulator (genetics) ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences - Abstract
The series of salts β′′-(BEDT-TTF)2[(H2O)(NH4)2M(C2O4)3]·18-crown-6 show ambient-pressure superconductivity when M = Cr, Rh. Evidence indicates that the previously reported Cr and Rh salts show a bulk Berezinski–Kosterlitz–Thouless superconducting transition. The isostructural ruthenium and iridium salts are reported here. The Ir salt represents the first radical-cation salt to contain a 5d tris(oxalato)metalate anion. The Ru and Ir salts do not show superconductivity but instead undergo a broad chemically induced metal to insulator transition at 155 K for ruthenium and at 100 K for iridium. The c axes of the Ru and Ir salts are much shorter than those of the Rh and Cr salts. Thus, the more stable metallic state of the Cr and Rh salts is associated with the more strongly 2D electronic systems. The different low-temperature behavior of the Ru and Ir salts, which exhibit a smaller interlayer spacing, could originate from a structural change in the anionic layer which thus can be easily transmitted to the donor layers and generate a localized state. However, another possibility is that it originates from Berezinski–Kosterlitz–Thouless effects., This work has been supported by a Royal Society Leverhulme Trust Senior Research Fellowship, and the JSPS (KAKENHI Grant Number JP17H01144) and Royal Society (Research Grants (RG100853 and RG081209), International Exchange Scheme (IE130367 and IE150152), and International Joint Project (JP0869972)). L.M. thanks the Royal Society and Leverhulme Trust for a Senior Research Fellowship. J.R.L. and L.M. thank Nottingham Trent University for Ph.D. funding. E.C. acknowledges support by the MICIU (Spain) through Grant PGC2018-096955-BC44 and the Severo Ochoa Centers of Excellence Program (Grant SEV-2015-0496) as well as by the Generalitat de Catalunya (2017SGR1506).
- Published
- 2019
44. Lattice and Charge Fluctuations in a Molecular Superconductor
- Author
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Hiroki Akutsu, Toshio Naito, Mikio Uruichi, Yasuhiro Nakazawa, and Takashi Yamamoto
- Subjects
Superconductivity ,Lattice (module) ,symbols.namesake ,Materials science ,Condensed matter physics ,Condensed Matter::Superconductivity ,symbols ,General Physics and Astronomy ,Superconducting transition temperature ,Condensed Matter::Strongly Correlated Electrons ,Charge (physics) ,Raman spectroscopy ,Astrophysics::Galaxy Astrophysics - Abstract
We report IR and Raman spectra for a two-dimensional superconductor, β′′-(BEDT-TTF)4[Ga(C2O4)3(H3O)]C6H5NO2, below the superconducting transition temperature. The behavior of the lattice-sensitive ...
- Published
- 2021
- Full Text
- View/download PDF
45. New Family of Six Stable Metals with a Nearly Isotropic Triangular Lattice of Organic Radical Cations and Diluted Paramagnetic System of Anions: κ(κ⊥)-(BDH-TTP)4MX4·Solv, where M = CoII, MnII; X = Cl, Br, and Solv = (H2O)5, (CH2X2)
- Author
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A. A. Bardin, Jun-ichi Yamada, and Hiroki Akutsu
- Subjects
Chemistry ,Isotropy ,Inorganic chemistry ,02 engineering and technology ,General Chemistry ,Electronic structure ,Crystal structure ,Conductivity ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Ion ,Paramagnetism ,Crystallography ,General Materials Science ,Hexagonal lattice ,Isostructural ,0210 nano-technology - Abstract
A new family of six paramagnetic metals, namely, κ-(BDH-TTP)4CoCl4·(H2O)5 (I), κ-(BDH-TTP)4Co0.54Mn0.46Cl4·(H2O)5 (II), κ-(BDH-TTP)4MnCl4·(H2O)5 (III), κ⊥-(BDH-TTP)4CoBr4·(CH2Cl2) (IV), κ⊥-(BDH-TTP)4MnBr4·(CH2Cl2) (V), and κ⊥-(BDH-TTP)4MnBr4·(CH2Br2) (VI), has been synthesized and characterized by X-ray crystallography, four-probe conductivity measurements, SQUID magnetometry, and calculations of electronic structure. The newly discovered κ⊥-type packing motif of organic layers differs from the parent κ-type by a series of longitudinal shifts of BDH-TTP radical cations in the crystal structure. Salts I–VI form two isostructural groups: I–III (κ) and IV–VI (κ⊥). Salts I–III are isostructural to the previously discovered κ-(BDH-TTP)2FeIIIX4 (X = Cl, Br) even though the charge of FeX4– anions is half that of the MX42– (M = Co, Mn) anions. The tetrahedral anions are disordered in I–III but completely ordered in IV–VI. The type of included solvent molecule is solely determined by the anion size. The paramagnet...
- Published
- 2016
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46. Thermal anomaly around the superconductive transition of κ-(BEDT-TTF)2Cu(NCS)2 with external pressure and magnetic field control
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Shusaku Imajo, Yuki Muraoka, Satoshi Yamashita, Yasuhiro Nakazawa, and Hiroki Akutsu
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Superconductivity ,Condensed matter physics ,Chemistry ,Transition temperature ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Heat capacity ,Magnetic field ,Condensed Matter::Superconductivity ,Phase (matter) ,0103 physical sciences ,Condensed Matter::Strongly Correlated Electrons ,Physical and Theoretical Chemistry ,Anomaly (physics) ,010306 general physics ,0210 nano-technology ,Ambient pressure ,Phase diagram - Abstract
The temperature dependence of the ac heat capacity of a molecule-based superconductor κ-(BEDT-TTF)2Cu(NCS)2 under external pressures and with magnetic fields is reported. A peak structure in C p T −1 due to the superconductive transition was observed around 9 K at ambient pressure. This peak is suppressed by applying magnetic fields up to 7 T. The systematic decrease in the transition temperature with the increase in external pressure is confirmed by thermodynamic measurements under 0.15, 0.30 and 0.45 GPa. Through the analysis of the peak shape of the thermal anomaly, it is suggested that the gradual suppression of the coupling strength of the superconductivity occurs with the increase in pressure. This feature is consistent with the argument based on the chemical pressure effect in the superconductive phase of κ-(BEDT-TTF)2 X system, where X denotes mono-valence counter anions. The result demonstrates that the appearance of the Fermi-liquid character produced by applying pressure in the dimer-Mott phase diagram affects the nature and the coupling feature of the superconductivity. Importance of high-pressure heat capacity for molecule-based compounds is emphasized.
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- 2016
- Full Text
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47. Variation of Electronic Heat Capacity of κ-(BEDT-TTF)2Cu[N(CN)2]Br Induced by Partial Substitution of Donor Layers
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Emre Yesil, Hiroki Akutsu, Tetsuya Nomoto, Yasuhiro Nakazawa, Shusaku Imajo, and Satoshi Yamashita
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Crystallography ,Materials science ,Organic superconductor ,General Physics and Astronomy ,Molecule ,Partial substitution ,Heat capacity - Abstract
Low temperature thermodynamic properties of an organic superconductor κ-[(BEDT-TTF)0.95(BEDSe-TTF)0.05]2Cu[N(CN)2]Br where 5% of donor molecules of κ-(BEDT-TTF)2Cu[N(CN)2]Br are substituted by BEDS...
- Published
- 2020
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48. Thermodynamic properties of glassy phonon states induced by strong electron correlations in 𝜃-type organic charge transfer salts
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Yasuhiro Nakazawa, Shinsuke Yamashita, Hiroki Akutsu, Tetsuya Nomoto, and E. Yesil
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chemistry.chemical_classification ,Materials science ,Phonon ,Salt (chemistry) ,Statistical and Nonlinear Physics ,Charge (physics) ,02 engineering and technology ,Electron ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,chemistry ,Chemical physics ,0103 physical sciences ,Condensed Matter::Strongly Correlated Electrons ,Boson peak ,010306 general physics ,0210 nano-technology - Abstract
The appearance of electron correlations–induced glassy state of low-energy phonons in the non-dimeric organic charge transfer salt in [Formula: see text]-(BEDT-TTF)2CsZn(SCN)4 is considered as a strong evidence of charge lattice coupling in molecular charge transfer salts. We discuss the temperature and the magnetic field dependences of the heat capacity of this salt in terms of the soft potential model to describe the thermodynamic properties of enhanced phonons that occur in molecular glasses. The evaluated [Formula: see text] term of [Formula: see text]-(BEDT-TTF)2CsZn(SCN)4 is about 30 mJ K[Formula: see text] mol[Formula: see text], which is much larger than other charge transfer salts described by the low-temperature approximation of the Debye model. The magnetic fields dependence of the boson peak is almost negligible, but the low-energy term, for example, in the temperature-linear term of heat capacity shows a slight change, probably due to the small amount of localized spin moments. The comparison with other systems is also performed.
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- 2020
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49. Development of frequency tuning AC modulation method for high-pressure heat capacity measurements of molecules-based compounds
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T. Maruyama, Hiroki Akutsu, Yasuhiro Nakazawa, Tetsuya Nomoto, and Shinsuke Yamashita
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Materials science ,business.industry ,Measure (physics) ,Statistical and Nonlinear Physics ,02 engineering and technology ,Calorimetry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Heat capacity ,Modulation ,High pressure ,0103 physical sciences ,Optoelectronics ,Molecule ,Development (differential geometry) ,Cube ,010306 general physics ,0210 nano-technology ,business - Abstract
The automatic frequency tuning method in the high-pressure ac calorimetry system constructed to measure heat capacity for molecules-based compounds with CuBe[Formula: see text]+[Formula: see text]NiCrAl cramp-type pressure cell is reported. This development is performed for increasing resolution and temperature ranges of the heat capacity measurements under external pressure up to 2.0 GPa. The system can check the appropriate conditions by tracing frequency dependence of [Formula: see text] to determine the oscillation frequency at the center of the plateau region of this value. The experiments using the powder samples of metal complexes clarified that the appropriate frequency changes sensitively depending on the difference of temperature and that of external pressures, especially at low temperature region. It decreases with increasing temperature and this relation was found to be almost linear with temperature in ambient pressure and under pressure conditions. The change of thermal diffusion from the sample part to the heat bath should be treated carefully in order to get enough resolution in high pressure AC heat capacity measurements of molecule-based compounds.
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- 2020
- Full Text
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50. Structure and properties of a BEDT-TTF-based organic conductor with a ferrocene-based magnetic anion octamethylferrocenedisulfonate
- Author
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Shin'ichi Nakatsuji, Yasuhiro Nakazawa, Jun-ichi Yamada, Scott S. Turner, Hiroki Akutsu, and Ryuichiro Hashimoto
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chemistry.chemical_classification ,Spins ,Chemistry ,business.industry ,Salt (chemistry) ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Ion ,Conductor ,Inorganic Chemistry ,chemistry.chemical_compound ,Crystallography ,Semiconductor ,Ferrocene ,0210 nano-technology ,business ,Tetrathiafulvalene - Abstract
The structure and properties of a new semiconducting BEDT-TTF-based charge-transfer salt containing the magnetic monoanion octamethylferrocenedisulfonate (–O3SC5( CH3)4Fe+C5(CH3)4-SO3 – (ofds)), -(BEDT-TTF)5(ofds)2 is described (BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene). The salt is a semiconductor with RT = 5.6 103 ·cm and Ea = 0.11 eV. There are two types of spins not only on the ferrocenyl parts but also the 2D donor layers. The former and latter spins obey Curie-Weiss (C = 0.721 emu K mol-1and = -5.5 K) and 2D Heisenberg (J2DH = - 80.3 K) models, respectively.
- Published
- 2018
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