Publications by authors named "Hiroshi Takatsu"

22 Publications

  • Page 1 of 1

Dehydration of Electrochemically Protonated Oxide: SrCoO with Square Spin Tubes.

J Am Chem Soc 2021 Oct 14;143(42):17517-17525. Epub 2021 Oct 14.

Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan.

Controlling oxygen deficiencies is essential for the development of novel chemical and physical properties such as high- superconductivity and low-dimensional magnetic phenomena. Among reduction methods, topochemical reactions using metal hydrides (e.g., CaH) are known as the most powerful method to obtain highly reduced oxides including NdSrNiO superconductor, though there are some limitations such as competition with oxyhydrides. Here we demonstrate that electrochemical protonation combined with thermal dehydration can yield highly reduced oxides: SrCoO thin films are converted to SrCoO by dehydration of HSrCoO at 350 °C. SrCoO forms square (or four-legged) spin tubes composed of tetrahedra, in contrast to the conventional infinite-layer structure. Detailed analyses suggest the importance of the destabilization of the SrCoO precursor by electrochemical protonation that can greatly alter reaction energy landscape and its gradual dehydration (HSrCoO) for the SrCoO formation. Given the applicability of electrochemical protonation to a variety of transition metal oxides, this simple process widens possibilities to explore novel functional oxides.
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http://dx.doi.org/10.1021/jacs.1c07043DOI Listing
October 2021

Electrochemical Crystal Growth of Titanium Oxyfluorides-A Strategy for Development of Electron-Doped Materials.

Inorg Chem 2021 Oct 31;60(19):14613-14621. Epub 2021 Aug 31.

Department of Materials and Life Chemistry, Faculty of Engineering, Kanagawa University, Yokohama, Kanagawa 221-8686, Japan.

We report on the growth of single crystals of an electron-doped titanium oxyfluoride, LiTi(O,F), employing high-temperature electrolysis of TiO with a eutectic LiMoO-LiF melt. Greenish octahedral-shaped crystals (∼30 μm in size) with a cubic rocksalt-type structure were successfully obtained by precisely tuning the applied voltage. The temperature-dependent magnetic susceptibility data revealed a paramagnetic behavior at low temperatures, ensuring the presence of Ti ions (mean valence number of +3.78; F/Ti ∼ 0.15). The crystals exhibited clear visible-light absorption and produced H from water in the presence of a sacrificial reagent under UV-light irradiation. LiTi(O,F) more efficiently produced H compared with a nondoped oxyfluoride LiTiOF, likely due to the doped electrons for the former. This work highlights a promising electrochemical approach toward growing electron-doped oxyfluoride crystals.
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http://dx.doi.org/10.1021/acs.inorgchem.1c01640DOI Listing
October 2021

Enhanced Magnetic Interaction by Face-Shared Hydride Anions in 6H-BaCrOH.

Inorg Chem 2021 Aug 26;60(16):11957-11963. Epub 2021 Jul 26.

Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan.

Studies on magnetic oxyhydrides have been almost limited to perovskite-based lattices with corner-sharing octahedra with a M-H-M (M: transition metal) angle of θ ∼ 180°. Using a high-pressure method, we prepared BaCrOH with a 6H-type hexagonal perovskite structure with corner- and face-sharing octahedra, offering a unique opportunity to investigate magnetic interactions based on a θ ∼ 90° case. Neutron diffraction for BaCrOH revealed an antiferromagnetic (AFM) order at ∼ 375 K, which is higher than ∼240 K in BaCrOF. The relatively high of BaCrOH can be explained by the preferred occupancy of H at the face-sharing site that provides AFM superexchange in addition to AFM direct exchange interactions. First-principles calculations on BaCrOH in comparison with BaCrOF and BaMnO further reveal that the direct Cr-Cr interaction is significantly enhanced by shortening the Cr-Cr distance due to the covalent nature of H. This study provides a useful strategy for the extensive control of magnetic interactions by exploiting the difference in the covalency of multiple anions.
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http://dx.doi.org/10.1021/acs.inorgchem.1c00992DOI Listing
August 2021

Spin Frustration in Double Perovskite Oxides and Oxynitrides: Enhanced Frustration in LaMnTaON with a Large Octahedral Rotation.

Inorg Chem 2021 Jun 24;60(11):8252-8258. Epub 2021 May 24.

Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan.

The B-site sublattice in the double perovskite oxides ABB'O (B: magnetic cation; B': nonmagnetic cation) causes spin frustration, but the relationship between the structure and spin frustration remains unclear although a number of compounds have been studied. The present study systematically investigated AMnB'O ( = 5/2) and found that the frustration factor, defined by = |θ|/ (θ: Weiss temperature; : Néel temperature), scales linearly with the tolerance factor , i.e., octahedral rotation. Unexpectedly, LaMnTaON (space group: 2/) synthesized under high pressure is more frustrated ( = 6) than oxides with similar values, despite the large octahedral rotation due to the small value of 0.914. Structural analysis suggests that the enhanced frustration can be attributed to the site preference of nitride anions at the equatorial positions, which reduces the variance of neighboring Mn-Mn distances. Our findings provide a new guide to control and improve spin frustration in double perovskites with multiple anions.
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http://dx.doi.org/10.1021/acs.inorgchem.1c00927DOI Listing
June 2021

Integrating molecular design and crystal engineering approaches in non-humidified intermediate-temperature proton conductors based on a Dawson-type polyoxometalate and poly(ethylene glycol) derivatives.

Nanoscale 2021 May 14;13(17):8049-8057. Epub 2021 Apr 14.

Department of Basic Science, School of Arts and Sciences, The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902, Japan.

Anionic metal-oxygen clusters known as polyoxometalates (POMs) have been widely researched as components of proton conductors. While proton conduction under non-humidified intermediate-temperature (100-250 °C) conditions is advantageous from the viewpoint of kinetics, few solid-state materials, not to mention POM-based crystals, show truly effective proton conduction without the aid of water vapor. In this context, non-volatile proton-conductive polymers have been confined into POM-based frameworks, while fast proton conduction was infeasible. Herein, we demonstrate a new strategy to synthesize POM-polymer composites exhibiting fast proton conduction under non-humidified intermediate-temperature conditions. Specifically, a molecular design approach utilizing poly(ethylene glycol)s (PEGs) of different terminal groups or chain lengths controls the proton carrier density, and a crystal engineering approach using a large Dawson-type POM ([α-PWO]) with an anisotropic molecular shape and alkali metal ions as counter cations fine-tunes the mobility of the confined PEGs as proton carriers. By integrating these approaches, proton conductivity over 10 S cm at 150 °C, comparable to the well-known highly proton-conductive solid-state materials, is achieved. The proton conduction mechanism is discussed with alternative current impedance spectroscopy jointly with specific heat capacity measurements and solid-state NMR spectroscopy.
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http://dx.doi.org/10.1039/d1nr01220gDOI Listing
May 2021

Strain-induced creation and switching of anion vacancy layers in perovskite oxynitrides.

Nat Commun 2020 Nov 23;11(1):5923. Epub 2020 Nov 23.

Department of Energy and Hydrocarbon Chemistry, Graduate school of Engineering, Graduate School of Engineering, Nishikyo-ku, Kyoto, 615-8510, Japan.

Perovskite oxides can host various anion-vacancy orders, which greatly change their properties, but the order pattern is still difficult to manipulate. Separately, lattice strain between thin film oxides and a substrate induces improved functions and novel states of matter, while little attention has been paid to changes in chemical composition. Here we combine these two aspects to achieve strain-induced creation and switching of anion-vacancy patterns in perovskite films. Epitaxial SrVO films are topochemically converted to anion-deficient oxynitrides by ammonia treatment, where the direction or periodicity of defect planes is altered depending on the substrate employed, unlike the known change in crystal orientation. First-principles calculations verified its biaxial strain effect. Like oxide heterostructures, the oxynitride has a superlattice of insulating and metallic blocks. Given the abundance of perovskite families, this study provides new opportunities to design superlattices by chemically modifying simple perovskite oxides with tunable anion-vacancy patterns through epitaxial lattice strain.
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http://dx.doi.org/10.1038/s41467-020-19217-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7683707PMC
November 2020

Epitaxial Stabilization of SrCuO with Infinite CuO Layers.

Inorg Chem 2020 Jul 8;59(14):10042-10047. Epub 2020 Jul 8.

Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan.

We report the epitaxial thin-film synthesis of SrCuO with infinitely stacked CuO layers composed of edge-sharing CuO square planes, using molecular-beam epitaxy. Experimental and theoretical characterizations showed that this material is a metastable phase that can exist by applying tensile biaxial strain from the (001)-SrTiO substrate. SrCuO shows an insulating electrical resistivity in accordance with the Cu valence state revealed by X-ray photoelectron spectroscopy. First-principles calculations also indicated that the unoccupied d band becomes substantially stabilized owing to the absence of apical anions, in contrast to ACuOCl (A = Sr, Ba) with an ACl block layer and therefore a -CuOCl octahedron. These results suggest that SrCuO is a suitable parent material for electron-doped superconductivity based on the CuO plane.
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http://dx.doi.org/10.1021/acs.inorgchem.0c01213DOI Listing
July 2020

Rattling Behavior in a Simple Perovskite NaWO.

Inorg Chem 2019 May 29;58(10):6790-6795. Epub 2019 Apr 29.

Graduate School of Engineering , Kyoto University , Kyoto 615-8510 , Japan.

Rattling phenomena have been observed in materials characterized by a large cage structure but not in a simple ABO-type perovskite because the size mismatch, if it exists, can be relieved by octahedral rotations. Here, we demonstrate that a stoichiometric perovskite oxide NaWO, prepared under high pressure, exhibits anharmonic phonon modes associated with low-energy rattling vibrations, leading to suppressed thermal conductivity. The structural analysis and the comparison with the ideal perovskite KWO without rattling behavior reveal that the presence of two crystallographic Na1 (2 a) and Na2 (6 b) sites in NaWO (space group Im3̅) accompanied by three in-phase WO octahedral (aaa) rotations generates an open space Δ ∼ 0.5 Å for the latter site, which is comparable with those of well-known cage compounds of clathrates and filled skutterudites. The observed rattling in NaWO is distinct from a quadruple perovskite AA'BO (A, A': transition metals) where the A (2 a) site with lower multiplicity is the rattler. The present finding offers a general guide to induce rattling of atoms in pristine ABO perovskites.
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http://dx.doi.org/10.1021/acs.inorgchem.9b00248DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7809913PMC
May 2019

High-Pressure Synthesis of Non-Stoichiometric Li WO (0.5 ≤ ≤ 1.0) with LiNbO Structure.

Inorganics (Basel) 2019 ;7(5)

Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan.

Compounds with the LiNbO-type structure are important for a variety of applications, such as piezoelectric sensors, while recent attention has been paid to magnetic and electronic properties. However, all the materials reported are stoichiometric. This work reports on the high-pressure synthesis of lithium tungsten bronze Li WO with the LiNbO-type structure, with a substantial non-stoichiometry (0.5 ≤ ≤ 1). LiWO exhibit a metallic conductivity. This phase is related to an ambient-pressure perovskite phase (0 ≤ ≤ 0.5) by the octahedral tilting switching between aaa and aaa.
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http://dx.doi.org/10.3390/inorganics7050063DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7067119PMC
January 2019

High-Pressure Synthesis of A NiO Ag Se (A=Sr, Ba) with a High-Spin Ni in Square-Planar Coordination.

Angew Chem Int Ed Engl 2019 Jan 17;58(3):756-759. Epub 2018 Dec 17.

Graduate School of Engineering, Kyoto University, Kyoto, 615-8510, Japan.

Square-planar coordinate Ni ions in oxides are exclusively limited to a low-spin state (S=0) owing to extensive crystal field splitting. Layered oxychalcogenides A Ni O Ag Se (A=Sr, Ba) with the S=1 NiO square lattice are now reported. The structural analysis revealed that the Ni ion is under-bonded by a significant tensile strain from neighboring Ag Se layers, leading to the reduction in crystal field splitting. Ba NiO Ag Se exhibits a G-type spin order at 130 K, indicating fairly strong in-plane interactions. The high-pressure synthesis employed here possibly assists the expansion of NiO square lattice by taking the advantage of the difference in compressibility in oxide and selenide layers.
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http://dx.doi.org/10.1002/anie.201810161DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6993455PMC
January 2019

Mixed-Spin Diamond Chain CuFePOF(HO) with a Noncollinear Spin Order and Possible Successive Phase Transitions.

Inorg Chem 2017 Aug 25;56(15):9353-9360. Epub 2017 Jul 25.

Graduate School of Engineering, Kyoto University , Kyoto 615-8510, Japan.

A diamond spin chain system, one of the one-dimensional frustrated lattices, is known to exhibit novel properties, but experimental studies have been exclusively confined to materials with a single spin component. Here, we report on the synthesis, structure, and magnetic properties of a new diamond chain compound CuFePOF(HO) 1 composed of mixed-spins of Cu (S = 1/2 × 2) and Fe (S = 5/2). Compound 1 crystallizes in the space group C2/c of the monoclinic crystal system with a = 7.7546(4) Å, b = 12.1290(6) Å, c = 9.9209(6) Å, β = 105.29(1)°, and Z = 4. DC magnetization, Mössbauer spectroscopy, and heat capacity measurements revealed an antiferromagnetic order at 11.3 K with a small ferromagnetic component. It is suggested that ferrimagnetic diamond chains are arranged in an antiferromagnetic fashion (i.e., [...Fe(↑)-2Cu(↓↓)-Fe(↑)...] and [...Fe(↓)-2Cu(↑↑)-Fe(↓)...]) within the ab plane to cancel net magnetization, and the spin orientation of the diamond chains changes alternately along the c axis due to the magnetic anisotropy, leading to a noncollinear spin order. Furthermore, another anomaly is observed in the heat capacity at around 3 K, suggesting a successive magnetic transition or crossover due to competing magnetic interactions.
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http://dx.doi.org/10.1021/acs.inorgchem.7b01533DOI Listing
August 2017

High-Pressure Synthesis of Fully Occupied Tetragonal and Cubic Tungsten Bronze Oxides.

Angew Chem Int Ed Engl 2017 05 24;56(21):5770-5773. Epub 2017 Apr 24.

Graduate School of Engineering, Kyoto University, Kyoto, 615-8510, Japan.

A high-pressure reaction yielded the fully occupied tetragonal tungsten bronze K W O (K WO ). The terminal phase shows an unusual transport property featuring slightly negative temperature-dependence in resistivity (dρ/dT<0) and a large Wilson ratio of R =3.2. Such anomalous metallic behavior possibly arises from the low-dimensional electronic structure with a van Hove singularity at the Fermi level and/or from enhanced magnetic fluctuations by geometrical frustration of the tungsten sublattice. The asymmetric nature of the tetragonal tungsten bronze K WO -K Ba WO phase diagram implies that superconductivity for x≤0.45 originates from the lattice instability because of potassium deficiency. A cubic perovskite KWO phase was also identified as a line phase-in marked contrast to Na WO and Li WO with varying quantities of x (<1). This study presents a versatile method by which the solubility limit of tungsten bronze oxides can be extended.
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http://dx.doi.org/10.1002/anie.201701732DOI Listing
May 2017

Electromagnon dispersion probed by inelastic X-ray scattering in LiCrO.

Nat Commun 2016 11 24;7:13547. Epub 2016 Nov 24.

Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, 5232 Villigen, Switzerland.

Inelastic X-ray scattering with meV energy resolution (IXS) is an ideal tool to measure collective excitations in solids and liquids. In non-resonant scattering condition, the cross-section is strongly dominated by lattice vibrations (phonons). However, it is possible to probe additional degrees of freedom such as magnetic fluctuations that are strongly coupled to the phonons. The IXS spectrum of the coupled system contains not only the phonon dispersion but also the so far undetected magnetic correlation function. Here we report the observation of strong magnon-phonon coupling in LiCrO that enables the measurement of magnetic correlations throughout the Brillouin zone via IXS. We find electromagnon excitations and electric dipole active two-magnon excitations in the magnetically ordered phase and heavily damped electromagnons in the paramagnetic phase of LiCrO. We predict that several (frustrated) magnets with dominant direct exchange and non-collinear magnetism show surprisingly large IXS cross-section for magnons and multi-magnon processes.
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http://dx.doi.org/10.1038/ncomms13547DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5123047PMC
November 2016

HfMnSb2 : A Metal-Ordered NiAs-type Pnictide with a Conical Spin Order.

Angew Chem Int Ed Engl 2016 08 29;55(34):9877-80. Epub 2016 Jun 29.

Graduate School of Engineering, Kyoto University, Kyoto, 615-8510, Japan.

The NiAs-type structure is one of the most common structures in solids, but metal order has been almost exclusively limited to chalcogenides. The synthesis of HfMnSb2 is reported with a novel metal-ordered NiAs-type structure. HfMnSb2 undergoes a conical spin order below 270 K, in marked contrast to conventional magnetic order observed in NiAs-type pnictides. We argue that the layered arrangement of Hf and Mn makes it a quasi 2D magnet, where the Mn layers with localized magnetic moments (Mn(2+) ; S=5/2) can interact only through RKKY interactions, instead of metal-metal bonding that is otherwise dominant for typical NiAs-type pnictides. This result suggests that controlling order-disorder in NiAs-type pnictides enables a study of 2D-to-3D crossover behavior in itinerant magnetic system.
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http://dx.doi.org/10.1002/anie.201602066DOI Listing
August 2016

Magnetic frustration, short-range correlations and the role of the paramagnetic Fermi surface of PdCrO2.

Sci Rep 2015 Jul 24;5:12428. Epub 2015 Jul 24.

Department of Physics, Tokyo Metropolitan University, Tokyo 192-0397, Japan.

Frustrated interactions exist throughout nature, with examples ranging from protein folding through to frustrated magnetic interactions. Whilst magnetic frustration is observed in numerous electrically insulating systems, in metals it is a rare phenomenon. The interplay of itinerant conduction electrons mediating interactions between localised magnetic moments with strong spin-orbit coupling is likely fundamental to these systems. Therefore, knowledge of the precise shape and topology of the Fermi surface is important in any explanation of the magnetic behaviour. PdCrO2, a frustrated metallic magnet, offers the opportunity to examine the relationship between magnetic frustration, short-range magnetic order and Fermi surface topology. By mapping the short-range order in reciprocal space and experimentally determining the electronic structure, we have identified the dual role played by the Cr electrons in which the itinerant ones on the nested paramagnetic Fermi surface mediate the frustrated magnetic interactions between local moments.
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http://dx.doi.org/10.1038/srep12428DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4513299PMC
July 2015

Extremely large magnetoresistance in the nonmagnetic metal PdCoO2.

Phys Rev Lett 2013 Aug 1;111(5):056601. Epub 2013 Aug 1.

Department of Physics, Tokyo Metropolitan University, Tokyo 192-0397, Japan.

Extremely large magnetoresistance is realized in the nonmagnetic layered metal PdCoO(2). In spite of a highly conducting metallic behavior with a simple quasi-two-dimensional hexagonal Fermi surface, the interlayer resistance reaches up to 35,000% for the field along the [11[over ¯]0] direction. Furthermore, the temperature dependence of the resistance becomes nonmetallic for this field direction, while it remains metallic for fields along the [110] direction. Such severe and anisotropic destruction of the interlayer coherence by a magnetic field on a simple Fermi surface is ascribable to orbital motion of carriers on the Fermi surface driven by the Lorentz force, but seems to have been largely overlooked until now.
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http://dx.doi.org/10.1103/PhysRevLett.111.056601DOI Listing
August 2013

Quantum oscillations and high carrier mobility in the delafossite PdCoO(2).

Phys Rev Lett 2012 Sep 10;109(11):116401. Epub 2012 Sep 10.

Scottish Universities Physics Alliance, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom.

We present de Haas-van Alphen and resistivity data on single crystals of the delafossite PdCoO(2). At 295 K we measure an in-plane resistivity of 2.6  μΩ cm, making PdCoO(2) the most conductive oxide known. The low-temperature in-plane resistivity has an activated rather than the usual T(5) temperature dependence, suggesting a gapping of effective scattering that is consistent with phonon drag. Below 10 K, the transport mean free path is ∼20  μm, approximately 10(5) lattice spacings and an astoundingly high value for flux-grown crystals. We discuss the origin of these properties in light of our data.
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http://dx.doi.org/10.1103/PhysRevLett.109.116401DOI Listing
September 2012

Quantum spin fluctuations in the spin-liquid state of Tb₂Ti₂O₇.

J Phys Condens Matter 2012 Feb 7;24(5):052201. Epub 2011 Dec 7.

Department of Physics, Tokyo Metropolitan University, Hachioji-shi, Tokyo 192-0397, Japan.

Neutron scattering experiments on a polycrystalline sample of the frustrated pyrochlore magnet Tb(2)Ti(2)O(7), which does not show any magnetic order down to 50 mK, have revealed that it shows condensation behavior below 0.4 K from a thermally fluctuating paramagnetic state to a spin-liquid ground state with quantum spin fluctuations. Energy spectra change from quasielastic scattering to a continuum with a double-peak structure at energies of 0 and 0.8 K in the spin-liquid state. Specific heat shows an anomaly at the crossover temperature.
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http://dx.doi.org/10.1088/0953-8984/24/5/052201DOI Listing
February 2012

Unconventional anomalous hall effect in the metallic triangular-lattice magnet PdCrO₂.

Phys Rev Lett 2010 Sep 20;105(13):137201. Epub 2010 Sep 20.

Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.

We experimentally reveal an unconventional anomalous Hall effect (UAHE) in a quasi-two-dimensional triangular-lattice antiferromagnet PdCrO₂. Using high quality single crystals of PdCrO₂, we found that the Hall resistivity ρ(xy) deviates from the conventional behavior below T*≃20 K, noticeably lower than T(N)=37.5 K, at which Cr³+ (S=3/2) spins order in a 120° structure. In view of the theoretical expectation that the spin chirality cancels out in the simplest 120° spin structure, we discuss required conditions for the emergence of UAHE within Berry-phase mechanisms.
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http://dx.doi.org/10.1103/PhysRevLett.105.137201DOI Listing
September 2010

Daphmanidins E and F, alkaloids from Daphniphyllum teijsmannii.

J Nat Prod 2006 Mar;69(3):418-20

Faculty of Pharmaceutical Sciences, Hoshi University, Tokyo, Japan.

Two new Daphniphyllum alkaloids, daphmanidins E (1) and F (2), have been isolated from the leaves of Daphniphyllum teijsmannii, and the structures were elucidated on the basis of spectroscopic data. Daphmanidins E and F showed a moderate vasorelaxant effect on rat aorta.
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http://dx.doi.org/10.1021/np0503799DOI Listing
March 2006

Daphmanidins C and D, novel pentacyclic alkaloids from Daphniphyllum teijsmanii.

Org Lett 2005 Feb;7(3):459-62

Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.

[structure: see text] Two novel alkaloids with an unprecedented fused-pentacyclic skeleton, daphmanidins C (1) and D (2), have been isolated from the leaves of Daphniphyllum teijsmanii, and the structures were elucidated on the basis of spectroscopic data. The relative stereochemistry of 1 and 2 was assigned by combination of NOESY correlations and a simulation analysis. Daphmanidin C (1) elevated activity of NGF biosynthesis.
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http://dx.doi.org/10.1021/ol047641+DOI Listing
February 2005

Daphniglaucins A and B, novel polycyclic quaternary alkaloids from Daphniphyllum glaucescens.

Org Lett 2003 May;5(10):1733-6

Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.

[structure: see text] Two cytotoxic quaternary Daphniphyllum alkaloids with an unprecedented fused-polycyclic skeleton containing a 1-azoniatetracyclo[5.2.2.0.(1,6)0.(4,9)]undecane ring system, daphniglaucins A (1) and B (2), have been isolated from the leaves of Daphniphyllum glaucescens. Their structures and relative stereochemistry were elucidated on the basis of spectroscopic data.
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http://dx.doi.org/10.1021/ol034388pDOI Listing
May 2003
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