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We present an organic compound exhibiting a spin-Peierls (SP) transition to an effective spin-1 antiferromagnetic uniform chain, that is, the Haldane chain. The clear disappearance of magnetization, accompanied by a structural phase transition, is well explained by the deformation to an effective spin-1 Haldane chain. The flexibility of the molecular orbitals in the organic radical compound allows the transformation of the exchange interactions into the Haldane state with different topologies. The SP transition in the present compound demonstrates a mechanism different from that of the conventional systems, paving another path for research in quantum phenomena originating from spin-lattice couplings., 6 pages, 3 figures

The A-site ordered chromate spinels LiGa1-xInxCr4O8 host a network of size-alternating spin-3/2 Cr3+ tetrahedra known as a 'breathing' pyrochlore lattice. For the x=0.05 composition, the complex magneto-structural ordering observed in the parent x=0 material is replaced by a single transition at Tf=11 K, ascribed to the collinear nematic order caused by strong spin-lattice coupling. We present here an inelastic neutron scattering study of the spin dynamics in this composition. Above Tf , the dynamical scattering function S(Q,E) is ungapped and quasi-elastic, similar to undoped LiGaCr4O8. Below Tf , the spectral weight splits between a broad inelastic feature at 5.8 meV and toward the elastic line. The former feature can be ascribed to spin precessions within antiferromagnetic loops, lifted to finite energy by the effective biquadratic spin-lattice term in the spin Hamiltonian.

We report on the high-pressure synthesis, crystal structure, and magnetic properties of four novel transition-metal oxyhydrides─Ba

We report dielectric, thermodynamical, acoustic, and optical properties of a chiral molecular crystal, 1,1'-bi-2-naphthol 2-dimethylsulfoxide (BINOL2DMSO). We find two successive phase transitions at Tc1=190 K and Tc2=125 K. The first transition at Tc1 is characterized by an order-disorder transition of the guest molecules DMSO along with ferroelectricity. At the second transition of Tc2, the crystal structure deforms from tetragonal to monoclinic, leading to domain formation. Low-temperature x-ray diffraction suggests that the space group changes from P4_12_12 (P4_32_12) to P4_1 (P4_3) at Tc1, and down to P112_1 at Tc2., 16 pages, 10 figures

An all-solid-state Li-ion secondary battery is a promising device that provides a solution to existing energy problems. However, it remains far from practical application mainly because of the lack of our basic understanding of the conduction mechanism of Li ions in Li-rich superionic conductors used as solid electrolytes in place of liquid electrolytes for conventional batteries. Herein, we studied the crystalline compound Li10GeP2S12 with the largest Li-ion conductivity thus far via a novel route based on a combination of single-crystal neutron diffraction experiments at low temperature and first-principles calculations, and found that a correlated migration of the densely packed Li ions governs the overall Li-ion conduction. The correlated migration mechanism provides us with guidelines on how to design efficient superionic conductors for more efficient batteries.

Sintered samples of a spinel oxide LiFeCr4O8, where Cr3+ and Fe3+ ions have localized moments, were found to show a large magnetic-field-induced volume increase approaching 500 ppm by applying a magnetic field of 9 T. This large volume increase appeared only at around 30 K. At 30 K, a spin-reorientation transition from ferrimagnetic to conical order occurs, giving rise to this large volume increase. The coexistence of ferrimagnetic and conical phases at this transition was found to be important, suggesting that such a large magnetic-field-induced volume change can be realized at various magnetic transitions in localized magnets with strong spin-lattice coupling., 6 pages, 4 figures, J. Phys. Soc. Jpn., accepted

We present the high-pressure synthesis and crystal structure of a novel titanium hydride complex, BaCa2Ti2H14, with 9-fold coordination. It comprises a unique dinuclear [Ti2H14]6– complex that cons...

Magnetic properties of an antiferromagnetic double perovskite oxide ${\mathrm{Ba}}_{2}{\mathrm{CaReO}}_{6}$, where ${\mathrm{Re}}^{6+}$ $(5{d}^{1})$ ions with large spin-orbit coupling are arranged on the face-centered-cubic lattice, are investigated using pulsed high magnetic field up to 66 T. Magnetization and magnetostriction measurements have revealed a magnetic field-induced phase transition at around 50 T. The phase transition accompanies a jump of magnetization and longitudinal magnetostriction of approximately $2\ifmmode\times\else\texttimes\fi{}{10}^{--4}$ with the change of power-law behavior, indicating sizable coupling between the electronic degrees of freedom and the lattice. The high-field phase exhibits a magnetic moment approximately 0.2 ${\ensuremath{\mu}}_{\mathrm{B}}$, which is close to the values observed in $5{d}^{1}$ double perovskite oxides with noncollinear magnetic structure. We argue that ${\mathrm{Ba}}_{2}{\mathrm{CaReO}}_{6}$ is an antiferromagnet that sits close to the phase boundary between the collinear and noncollinear phases, providing the target material for investigating the interplay between spin-orbital entangled electrons and magnetic field.

Substitution effects of Os for Ru in ��-RuCl3 are investigated in a wide composition range of 0 =< x =< 0.67 in Ru1-xOsxCl3 by X-ray and electron diffraction, magnetic susceptibility, heat capacity, and Raman spectroscopy measurements. Apart from the Kitaev physics with antiferromagnetic interactions increasing with x, a rich phase diagram is obtained, which includes an antiferromagnetic long-range order below 12 K for x =< 0.15, a dome-shaped spin-singlet dimer phase below 130 K for 0.15 =< x =< 0.40, and a magnetic short-range order for x > 0.40. A dimerization as similarly observed in ��-RuCl3 under high pressure occurs in the spin-singlet phase. It is suggested that Ru-Os pairs in the solid solutions tend to form dimers with short bonds and trigger the first-order transition in the presence of pseudo-threefold rotational symmetry for dimerization around a substituted Os atom only at low substitutions. This is a rare example of molecular orbital crystallization induced by elemental substitution in a highly disordered system. The short-range order at high substitutions may be related to a random-singlet state stabilized by bond disorder in the honeycomb net., 13 pages, 14 figures

We have successfully synthesized a hyperkagome antiferromagnet ${\mathrm{Zn}}_{2}{\mathrm{Mn}}_{3}{\mathrm{O}}_{8}$ by a topochemical method, where ${\mathrm{Mn}}^{4+}$ ions with $S=3/2$ spins form a three-dimensional (3D) corner-sharing triangle network. Magnetic susceptibility and heat capacity measurements revealed an antiferromagnetic transition at ${T}_{\mathrm{N}}=5.8\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. Although no evidence was found for any structural distortion accompanying the transition, the low-temperature magnetic heat capacity showed a nearly ${T}^{2}$ dependence, suggesting the realization of a 2D magnonlike excitation in the 3D hyperkagome lattice.

The discovery of new extended structures has often led to the development of new fields in chemistry and physics. However, the numerous combinations of metals (or cations) to yield new materials ha...

Single crystals of the lithium-ion conductor Li10GeP2S12 have been successfully grown by the self-flux method and are studied by means of X-ray diffraction and impedance spectroscopy. The weak anis...

We devised a portable system that generates pulsed high magnetic fields up to 77 T with 3 $\mu$s duration. The system employs the single turn coil method, a destructive way of field generation. The system consists of a capacitor of 10.4 $\mu$F, a 30 kV charger, a mono air-gap switch, a triggering system, and a magnet clamp, which weighs less than 1.0 tons in total and is transportable. The system offers opportunities for single-shot experiments at ultrahigh magnetic fields in combinations with novel quantum beams. The single-shot x-ray diffraction experiment using x-ray free-electron laser at 65 T is presented. We comment on the possible update of the system for the generation of 100 T., Comment: 5 pages, 4 figures

Making and breaking bonds in a solid-state compound greatly influences physical properties. A well-known playground for such bonding manipulation is the ThCr

We report the synthesis, crystal structure, and magnetic properties of two new quantum antiferromagnets A3ReO5Cl2 (A = Sr and Ba). The crystal structure is isostructural with the mineral pinalite Pb3WO5Cl2, in which the Re6+ ion is square-pyramidally coordinated by five oxide atoms, and forms an anisotropic triangular lattice (ATL) made of S = 1/2 spins. The magnetic interactions J and J' in the ATL are estimated from magnetic susceptibilities to be 19.5 (44.9) and 9.2 (19.3) K, respectively, with J'/J = 0.47 (0.43) for A = Ba (Sr). For each compound, heat capacity at low temperatures shows a large T-linear component with no signature of long-range magnetic order above 2 K, which suggests a gapless spin liquid state of one-dimensional character of the J chains in spite of the significantly large J' couplings. This is a consequence of one-dimensionalization by geometrical frustration in the ATL magnet; a similar phenomenon has been observed in two compounds with slightly smaller J'/J values: Cs2CuCl4 (J'/J = 0.3) and the related compound Ca3ReO5Cl2 (0.32). Our findings demonstrate that 5d mixed-anion compounds provide a unique opportunity to explore novel quantum magnetism., Comment: 24 pages, 7 figures, 2 Tables

Magnetic and structural properties of double perovskite type bromides Cs

We report the synthesis, crystal structure, and magnetic properties of the two new quantum antiferromagnets A

Structural and magnetic properties of cubic spinel selenides $\mathrm{Ga}{M}_{4}{\mathrm{Se}}_{8}$ ($M=\mathrm{Nb}$, Ta), which are candidates for the molecular ${J}_{\mathrm{eff}}=3/2$ Mott insulators, are investigated. The effective magnetic moments are reduced compared to the spin only value, indicating the presence of sizable spin-orbit coupling. ${\mathrm{GaNb}}_{4}{\mathrm{Se}}_{8}$ and ${\mathrm{GaTa}}_{4}{\mathrm{Se}}_{8}$ exhibit phase transitions into the nonmagnetic ground states with orthorhombic and tetragonal structures, respectively, which are robust against magnetic field up to at least 60 T. A cubic-cubic phase transition is observed in ${\mathrm{GaNb}}_{4}{\mathrm{Se}}_{8}$ preceding the magnetic transition, suggesting the existence of a quadrupolar-ordered phase theoretically predicted in the ${J}_{\mathrm{eff}}=3/2$ Mott insulator.

Single shot x-ray diffraction (XRD) experiments have been performed with a x-ray free electron laser (XFEL) under pulsed high magnetic fields up to 16 T generated with a nondestructive minicoil. The antiferromagnetic insulator phase in a perovskite manganaite, Pr$_{0.6}$Ca$_{0.4}$MnO$_{3}$, is collapsed at a magnetic field of $\approx 8$ T with an emergence of the ferromagnetic metallic phase, which is observed via the accompanying lattice changes in a series of the single shot XRD. The feasibility of the single shot XRD experiment under ultrahigh magnetic fields beyond 100 T is discussed, which is generated with a portable destructive pulse magnet., 6 pages, 5 figures

We study the lead rhenium oxide PbRe2O6 as a candidate spin–orbit-coupled metal (SOCM), which has attracted much attention as a testing ground for studying unconventional Fermi liquid instability associated with a large spin–orbit interaction. The compound comprises a stack of modulated honeycomb lattices made of Re5+ (5d2) ions in a centrosymmetric R–3m structure at room temperature. Resistivity, magnetic susceptibility, and heat capacity measurements using single crystals reveal two successive first-order phase transitions at Ts1 ​= ​265 ​K and Ts2 ​= ​123 ​K. At Ts1, the magnetic susceptibility is enormously reduced and a structural transition to a monoclinic structure takes place, while relatively small changes are observed at Ts2. Surprisingly, PbRe2O6 bears a close resemblance to another SOCM candidate Cd2Re2O7 despite crucial differences in the crystal structure and probably in the electronic structure, suggesting that PbRe2O6 is an SOCM.

We present the high-pressure synthesis and crystal structure of a novel titanium hydride complex, BaCa

We report thermal expansion and magnetostriction in breathing pyrochlore magnets LiACr$_4$X$_8$ (A = Ga, In, X = O, S) measured by a dilatometric method on sintered samples. All four of these compounds showed a large volume contraction associated with antiferromagnetic order with decreasing temperature. Above the Ne\'el temperature, LiGaCr4S8 showed negative thermal expansion, LiInCr4O8 showed positive thermal expansion with concave-downward temperature dependence, and LiInCr4S8 showed positive forced volume magnetostriction. All these phenomena are likely caused by the complex structure-magnetism correlation within the breathing pyrochlore structure with J and J'. These results suggested that breathing pyrochlore magnets are promising for the realization of various volumetric phenomena related to their magnetism not only in the magnetically-ordered phase but also in the paramagnetic phase., Comment: 5 pages, 3 figures, Journal of the Physical Society of Japan, in press

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

Recently, the anomalous two-fold-symmetric in-plane anisotropy of superconducting states has been observed in a layered superconductor system, LaO1&minus, xFxBiSSe (x = 0.1 and 0.5), with a tetragonal (four-fold symmetric) in-plane structure. To understand the origin of the phenomena observed in LaO1&minus, xFxBiSSe, clarification of the low-temperature structural phase diagram is needed. In this study, we have investigated the low-temperature crystal structure of LaO1&minus, xFxBiSSe (x = 0, 0.01, 0.02, 0.03, and 0.5). From synchrotron X-ray diffraction experiments, a structural transition from tetragonal to monoclinic was observed for x = 0 and 0.01 at 340 and 240 K, respectively. For x = 0.03, a structural transition and broadening of the diffraction peak were not observed down to 100 K. These facts suggest that the structural transition could be suppressed by 3% F substitution in LaO1&minus, xFxBiSSe. Furthermore, the crystal structure for x = 0.5 at 4 K was examined by low-temperature laboratory X-ray diffraction, which confirmed that the tetragonal structure is maintained at 4 K for x = 0.5. Our structural investigation suggests that the two-fold-symmetric in-plane anisotropy of superconducting states observed in LaO1&minus, xFxBiSSe was not originated from structural symmetry lowering in its average structure. To evaluate the possibility of the local structural modification like nanoscale puddles in the average tetragonal structure, further experiments are desired.

We investigated the magnetic and structural transitions of $\mathrm{M}{\mathrm{n}}_{1\ensuremath{-}x}\mathrm{M}{\mathrm{g}}_{x}{\mathrm{V}}_{2}{\mathrm{O}}_{4}\phantom{\rule{4pt}{0ex}}(x=0$, 0.05, 0.1, 0.15) single crystals with a normal spinel structure. These crystals all exhibit a cubic-to-tetragonal structural transition at ${T}_{\mathrm{S}}$ caused by the orbital ordering of ${\mathrm{V}}^{3+}$ ions, which is followed by a ferrimagnetic ordering transition at ${T}_{\mathrm{M}}$. We found that ${T}_{\mathrm{M}}$ is equal to ${T}_{\mathrm{S}}$ for $x\ensuremath{\le}0.1$, but the ferrimagnetic transition is shifted to lower temperature by Mg doping and ${T}_{\mathrm{S}}$ and ${T}_{\mathrm{M}}$ can be separated clearly for $x=0.15$. Moreover, a certain degree of orbital fluctuations was brought about by the ferrimagnetic transition at ${T}_{\mathrm{M}}$, but suppressed below ${T}^{*}$, leading to another transition from weak orbital fluctuations to further orbital ordering at ${T}^{*}$. The orbital fluctuations were caused by the anomalous interchain interaction ${J}^{\mathrm{c}}$ and can be also enhanced by the substitution of Mg for Mn due to the decrease of the distance between ${\mathrm{V}}^{3+}$ ions along the $c$ direction ${}^{\phantom{\rule{4pt}{0ex}}c}{R}_{\mathrm{v}\text{\ensuremath{-}}\mathrm{v}}$, which results in the increase of ${J}^{\mathrm{c}}$.

High magnetic field x-ray diffraction experiments of solid oxygen have been performed at 10 K using DC magnetic fields of up to 5 T as well as pulsed magnetic fields of up to 25 T. The $\ensuremath{\alpha}$ phase of oxygen exhibits no magnetostriction greater than $\mathrm{\ensuremath{\Delta}}d/d={10}^{\ensuremath{-}4}$ at 5 T, where $d$ and $\mathrm{\ensuremath{\Delta}}d$ denote a lattice plane spacing and its magnetic field variation, respectively. The $\mathrm{\ensuremath{\Delta}}d/d$ at higher fields of up to 25 T is found to be smaller than $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$. These results contradict the previously reported giant magnetostriction in the $\ensuremath{\alpha}$ phase where the volume magnetostriction $\mathrm{\ensuremath{\Delta}}V/V$ reaches ${10}^{\ensuremath{-}2}$ at 7.5 T [K. Katsumata et al., J. Phys.: Condens. Matter 17, L235 (2005)].

For the Fukushima decommissioning, the distribution of boron species in the fuel debris must be determined to assess the risk of recriticality, the debris hardness and thus complicate its successful retrieval. As a result, the relocation behavior of boron carbide (B4C) control rod materials has attracted significant attention. In this work, the influence of the thickness of its stainless steel (SS) clad on the initial relocation behavior of the control rod was investigated. In particular, the initial relocation behavior of the B4C control rod materials was dynamically visualized using a technique previously developed by the authors. To simulate the control rod, a type-304 SS tube filled with B4C powder containing particles with sizes of approximately 20–30 µm was heated to a temperature exceeding its eutectic point (1473 K). The three relocation modes of the obtained eutectic melt corresponded to film formation, droplet formation without collapse and droplet formation with collapse.

We investigated topochemical anion exchange reactions for a ScIII-substituted SrTiIVO3 perovskite, Sr(Ti1–yScy)O3–y/2□y/2 (y ≤ 0.1), using CaH2. It was found that the initial introduction of a small amount of anion vacancies (y/2) is crucial to enhance the anion (H–/O2–) exchangeability. For example, hydride reduction of Sr(Ti0.95Sc0.05)O2.975 yielded the oxyhydride SrTi0.95Sc0.05O2.56H0.41 in which the hydride concentration is increased by 33% with respect to pristine SrTiO3 (leading to SrTiO2.76H0.24). This observation highlights the importance of anion vacancies to improve anion (H–/O2–) diffusion, which is a well-known strategy for improving oxide anion conductivity, and suggests that such a vacancy-assisted reaction could be applied to other anion exchange reactions (e.g., F–/O2– and N3–/O2–) to extend the solubility range.

Single crystals are indispensable for understanding the fundamental properties of materials, although obtaining them are often challenging. To investigate the magnetic properties of a kagome-lattice antiferromagnet, we have performed a topochemical crystal transformation from a copper mineral volborthite with a distorted kagome lattice into another copper mineral vesignieite with an almost perfect kagome lattice. A millimeter-sized crystal of vesignieite, which is difficult to prepare via direct chemical reactions, has been successfully obtained. Magnetization measurements on the crystals reveal a unique magnetic order with weak-ferromagnetic moments lying within the kagome plane and successive anomalies in the magnetization curve, which would give important information on the magnetic order of the kagome-lattice antiferromagnet. The present results demonstrate a novel route via the topochemical crystal transformation in preparing a hard-to-obtain crystal.

We investigate the low temperature anion exchange behavior of hydride and oxide in perovskite oxynitrides. CaH 2 reduction of (Sr 1– x La x )Ti(O 3 –x N x ) (0 x ≤ 1) resulted in the selective anion exchange of hydride for oxide rather than nitride, yielding the oxyhydride-nitride (Sr 1– x La x )Ti(O 3 –x–y H y N x ). However, the exchange of hydride is drastically suppressed with increasing nitrogen content and is completely impeded when the nitride content reaches 10% of the anionic site. This implies that the N 3– anions in the oxide lattice play a crucial role in lowering diffusion of O 2– (and H – ). The present study indicates the necessity to consider kinetic aspects when manipulating anion compositions, in particular in a mixed anion system with a small amount of anion vacancies.

Layered materials embrace rich intercalation reactions to accommodate high concentrations of foreign species within their structures, and find many applications spanning from energy storage, ion exchange to secondary batteries. Light alkali metals are generally most easily intercalated due to their light mass, high charge/volume ratio and in many cases strong reducing properties. An evolving area of materials chemistry, however, is to capture metals selectively, which is of technological and environmental significance but rather unexplored. Here we show that the layered telluride T[2]PTe[2] (T=Ti, Zr) displays exclusive insertion of transition metals (for example, Cd, Zn) as opposed to alkali cations, with tetrahedral coordination preference to tellurium. Interestingly, the intercalation reactions proceed in solid state and at surprisingly low temperatures (for example, 80 °C for cadmium in Ti[2]PTe[2]). The current method of controlling selectivity provides opportunities in the search for new materials for various applications that used to be possible only in a liquid., 重金属を固体中で選択的に吸収する材料の発見 : 電子機器からの新たな金属回収法などの開発に期待. 京都大学プレスリリース. 2016-12-20.

The semimetallic behavior of the so-called ``failed Kondo insulator'' CeNiSn has been ascribed to a nodal line in the Kondo hybridization derived from a particular symmetry of the Ce $4f$ orbitals ground state. Here we investigate the geometry of the CeNiSn conduction band by combined angle-resolved photoemission spectroscopy (ARPES) in the high-temperature regime and Open core generalized gradient approximation plus spin-orbit coupling calculations, in order to determine how the nodal hybridization takes place. We identify the Fermi sheet involved in the semimetallic regime from its locus and its shape, respectively, in agreement with the expected nodal line and with quantum oscillations. We further extrapolate and discuss the low-temperature Fermi surface in terms of the expected nodal hybridization with a localized $f$-level. The obtained hypothetical low-temperature Fermi surface is compatible with the description from quantum oscillations, and with both the highly anisotropic magnetoresistance and the isotropic Nernst effect. This work offers an overview of the conduction band of CeNiSn before hybridization, and it paves the way to a definitive understanding of its low-temperature state. In addition, this work serves as a basis for more challenging low-temperature ARPES measurements.