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Electronic-state modulation utilizing the electrostatic properties and dynamics of hydrogen-bonding (H-bonding) protons is an effective strategy for realizing novel electron–proton-coupled functionalities. However, material developments based on this strategy have been limited to a few π-electron systems; thus, the realization of solid-state electron–proton-coupled functionalities is challenging. Here, we successfully synthesized new crystals based on nickel catecholdithiolene complexes, which are d/π-electron systems with H-bonds, exhibiting various deprotonation/oxidation states brought about via solution processes. In these crystals, unique three-dimensional framework or two-dimensional sheet structures are formed by intermolecular H-bonds between the complexes, including anionic [O–H⋯O]− H-bonds (dO⋯O ∼ 2.59 A), which were advantageous for proton transfer in solid states. Importantly, detailed analyses revealed that the nickel complexes in the crystals were in various oxidation/deprotonation states. Accordingly, the magnetic properties changed from paramagnetic to non-magnetic with the oxidation of the complexes through proton-coupled electron transfer in solution processes. Density functional theory calculations revealed that the d/π electronic states of the nickel complexes in each crystal are significantly modulated depending on the deprotonation/oxidation states. We propose a possible mechanism for the oxidation-coupled deprotonation of the nickel complex, where various oxidation/deprotonation states can be obtained as crystals and controlled by recrystallization conditions, which is realized by the characteristic d/π-conjugation property and (de)protonation/redox activity of the nickel catecholdithiolene complex. The findings provide a further possibility to construct d/π-electron–proton-coupled collective functionalities based on this complex, together with significant insights for exploring novel electron–proton-coupled functionalities in the solid state.

We investigated the multiscale characters of the crystal structure of the oxynitride perovskite LaTiO2N. While X-ray diffraction results identified the average structure as being centrosymmetric, we detected a signature of unknown structural deformation. By viewing the local structure, we unveiled the formation of a polar structure at the nanoscale.

Purely organic crystals, κ-X3(Cat-EDT-TTF)2 [X = H or D, Cat-EDT-TTF = catechol-fused tetrathiafulvalene], are a new type of molecular conductor with hydrogen dynamics. In this work, hydrostatic pressure effects on these materials were investigated in terms of the electrical resistivity and crystal structure. The results indicate that the pressure induces and promotes hydrogen (deuterium) localization in the hydrogen bond, in contrast to the case of the conventional hydrogen-bonded materials (where pressure prevents hydrogen localization), and consequently leads to a significant change in the electrical conducting properties (i.e., the occurrence of a semiconductor–insulator transition). Therefore, we have successfully found a new type of pressure-induced phase transition where the cooperation of the hydrogen dynamics and π-electron interactions plays a crucial role.

We have designed and synthesized a novel metal dithiolene complex with hydrogen-bonding (H-bonding) ability, [Au(catdt)2]− (catdt: catechol-4,5-dithiolate) and successfully constructed [Au(catdt)2]−-based three-dimensional (3D) anionic molecular frameworks in two kinds of salts, (Ph4P)[Au(catdt)2]·0.5H2O (3a) and (Ph4P)[Au(catdt)2]·Et2O·n(solv) (3b; solv = Et2O and/or acetone). To our knowledge, these are the first examples of the 3D molecular frameworks based on H-bonded metal dithiolene complexes. Importantly, these frameworks are constructed through 3D intermolecular H-bonds between [Au(catdt)2]− molecules, and have tubular channels occupied by large Ph4P+ cations, where multiple cation–anion short contacts are formed to stabilize the 3D framework structures. Furthermore, in addition to 3a and 3b with 3D frameworks, we have obtained (Ph4P)[Au(catdt)2]·2THF (3c) having a 2D layered structure. A detailed comparison of the structures of these compounds reveals that the included solvent molecules play an important role in regulating the intermolecular interactions and assembled structures. Interestingly, we have found that, due to the differences in the H-bonding ability and molecular size of H2O and Et2O, the wall structures of the 3D frameworks in 3a without voids and 3b with voids are qualitatively different.

Anthracene, a simple planar building block for organic semiconductors, shows strong intermolecular interactions and exhibits strong blue fluorescence. Thus, its derivatives have a great potential to integrate considerable charge carrier mobility and strong emission within a molecule. Here, we systematically studied the influence of alkyl chain length on the crystal structures, thermal properties, photophysical characteristics, electrochemical behaviors, and mobilities for a series of 2,6-di(4-alkyl-phenyl)anthracenes (Cn-Ph-Ants, where n represents the alkyl chain length). Among them, Cn-Ph-Ants (n = 0, 1, 2, and 3) display similar layered herringbone (LHB) packing motifs, which facilitate two-dimensional charge transport and thereby enables high-performance organic field-effect transistors (OFETs). All Cn-Ph-Ants exhibit similar work functions and show strong blue fluorescence with photoluminescence quantum yields (PLQY) of approximately 40% in toluene. In addition, the absolute powder PLQYs of C0-, C2-, C3-, C4-, and C6-Ph-Ants are 24.6, 8.2, 5.7, 10.9, and 8.6%, respectively. Note that the alkyl chain length shows a significant effect on the charge mobilities of Cn-Ph-Ants. Our newly synthesized C1-, C3-, and C4-Ph-Ants show hole mobilities of up to 2.40, 1.34, and 1.00 cm2 V-1 s-1, respectively, with mobilities of 3.40, 1.57, and 0.82 cm2 V-1 s-1 for C0-, C2-, and C6-Ph-Ants, indicating an increasing tendency of mobility with shorter alkyl chain length. This feature is related to the microstructures of the thin films, which reveal the enhanced film order, crystallinity, and grain size with a decrease in the alkyl chain length. Moreover, we theoretically analyze the intermolecular transfer integrals of HOMOs, which increase at T-shaped contacts as the alkyl chain length decreases, which improves the intermolecular charge transport properties, leading to the increases in mobility. Interestingly, the anisotropy of the transfer integral tends to decrease upon substitution with longer alkyl chains, suggesting that alkyl chain adjustments may facilitate isotropic charge transport property in 2,6-alkylated anthracenes.

High critical temperature (Tc) superconductivity is generally considered to result from a fluctuation-mediated Cooper-pairing derived from a parent phase. The question of what type of fluctuation forms in materials thus plays a key role in understanding the mechanism of superconductivity. The iron-based superconductor LaFeAsO1-xHx possesses bipartite magnetic parent phases with centrosymmetric (x ~ 0) and non-centrosymmetric (x ~ 0.5) structures. The latter is an intriguing polar-metal phase induced by temperature and carrier doping. Here, we investigate average and local structures of LaFeAsO1-xHx using X-ray diffraction and extended X-ray absorption fine-structure measurements. We found lattice C4 symmetry breaking far above the structural transition temperature, and the signature of a tiny split in As–Fe bond distances with broken spatial inversion symmetry in a wide temperature/doping range. The former reveals a nematic state, and the latter highlights a fluctuated state of polar structure which can be appropriately called polar nematic state.

We report the epitaxial growth of Ca 3 SnO antiperovskite oxide films on (0 0 1)-oriented cubic yttria-stabilized zirconia (YSZ) substrates by using a conventional pulsed laser deposition (PLD) technique. In this work, a sintered Ca 3 SnO pellet is used as the ablation target. X-ray diffraction measurements demonstrate the (0 0 1) growth of Ca 3 SnO films with the antiperovskite structure and a cube-on-cube orientation relationship to the YSZ substrate. The successful synthesis of the antiperovskite phase is further confirmed by X-ray photoemission spectroscopy. These results strongly suggest that antiperovskite-oxide films can be directly grown on substrates from the target material using a PLD technique.

Formamidinium [FA, HC(NH2)2+] lead iodide and its cation mixture have attracted interest as potentials in applications for efficient solar cells superior to well-known methylammonium lead iodide. W...

The charge disproportionation of Mn $3d$ and O $2p$ electronic states was investigated in two $({\mathrm{LaMnO}}_{3}{)}_{2}{({\mathrm{SrMnO}}_{3})}_{2}$ superlattices using the resonant x-ray scattering technique. The superlattices show significantly different conductivity even with the same composition. The large modulation of the Mn $3d$ electronic state was observed in the insulating sample, however the charge disproportionation and magnetic modulation of O $2p$ were shown in the semiconductive sample. It is suggested that the charge modulation appears in either Mn $3d$ or O $2p$, which is strongly related to strength of the $p\text{\ensuremath{-}}d$ hybridization, which is the main factor determining the electric conductivity in the superlattices.

L12-ordered CoPt3 and L10-ordered CoPt are formed in electron-beam-deposited (Co/Pt)4 multilayer thin films with and without a Ti underlayer, respectively, on Si/SiO2 substrates by rapid thermal annealing. The crystal structures, magnetic properties, and surface morphologies of the films are investigated by grazing incidence X-ray diffraction (GI-XRD), vibrating sample magnetometer (VSM), and scanning electron microscope (SEM), respectively. In the film without a Ti underlayer, L10-ordered CoPt with an isolated round grain structure is confirmed, showing an in-plane coercivity of 2.7 kOe. In contrast, in the film with a Ti underlayer, L12-ordered CoPt3 is confirmed together with Co-rich A1-disordered CoPt, showing an in-plane coercivity of 500 Oe, which exhibits an angular-outlined continuous film structure. The three sets of experimental results from GI-XRD, VSM, and SEM coincide well with each other.

We report that the volume of an orbital-ordered Mott insulator Ca2RuO4 is purely changed by an electrical current at constant temperature and pressure. The observed giant electromechanical response...

We investigate the thickness effects on charge and magnetic orderings in Fe perovskite oxide ${\mathrm{La}}_{1/3}{\mathrm{Sr}}_{2/3}{\mathrm{FeO}}_{3}/{\mathrm{SrTiO}}_{3}$ thin films by hard x-ray and resonant soft x-ray scattering (RSXS) with changing thin-film thickness systematically. We found that the correlation lengths of the magnetic ordering along the in-plane and out-of-plane directions are comparable and proportional to the thickness, and show stronger thickness dependence than those of charge ordering. The magnetic ordered states disappear when the correlation length of magnetic ordering decreases to that of charge ordering through the intrinsic thickness effects. Surface-sensitive grazing-incident RSXS revealed that the orderings exist even in the surface region, which indicates that the observed orderings are not affected by surface effects like oxygen vacancies. Critical thickness is in 5--15 nm, which corresponds to 4--11 antiferromagnetic ordering period. This critical value seems to be common to other ferromagnetic oxide thin films.

K3Cu3AlO2(SO4)4 is a highly one-dimensional spin-1/2 inequilateral diamond-chain antiferromagnet. Spinon continuum and spin-singlet dimer excitations are observed in the inelastic neutron scattering spectra, which is in excellent agreement with a theoretical prediction: a dimer-monomer composite structure, where the dimer is caused by strong antiferromagnetic (AFM) coupling and the monomer forms an almost isolated quantum AFM chain controlling low-energy excitations. Moreover, muon spin rotation/relaxation spectroscopy shows no long-range ordering down to 90 mK, which is roughly three orders of magnitude lower than the exchange interaction of the quantum AFM chain. K3Cu3AlO2(SO4)4 is, thus, regarded as a compound that exhibits a Tomonaga-Luttinger spin liquid behavior at low temperatures close to the ground state.

Two-dimensional (2D) electrides are a new concept material in which anionic electrons are confined in the interlayer space between positively charged layers. We have carried out angle-resolved photoemission spectroscopy measurements on ${\mathrm{Y}}_{2}\mathrm{C}$, which is a possible 2D electride, in order to verify the formation of 2D electride states in ${\mathrm{Y}}_{2}\mathrm{C}$. We clearly observe the existence of semimetallic ``electride bands'' near the Fermi level, as predicted by ab initio calculations, which conclusively demonstrates that ${\mathrm{Y}}_{2}\mathrm{C}$ is a quasi-2D electride with electride bands derived from interlayer anionic electrons.

A systematic study of the crystal structure of a layered iron oxypnictide LaFeAsO1−xHx as a function of pressure was performed using synchrotron X-ray diffraction. This compound exhibits a unique phase diagram of two superconducting phases and two parent phases. We established that the As–Fe–As angle of the FeAs4 tetrahedron widens on the application of pressure due to the interspace between the layers being nearly infilled by the large La and As atoms. Such rarely observed behaviour in iron pnictides implies that the FeAs4 coordination deviates from the regular tetrahedron in the present systems. This breaks a widely accepted structural guide that the superconductivity favours the regular tetrahedron, albeit the superconducting transition temperature (Tc) increases from 18 K at ambient pressure to 52 K at 6 GPa for x = 0.2. In the phase diagram, the second parent phase at x ~ 0.5 is suppressed by pressure as low as ~1.5 GPa in contrast to the first parent phase at x ~ 0, which is robust against pressure. We suggest that certain spin-fluctuation from the second parent phase is strongly related to high-Tc under pressure.

Ordering and disordering electrons When a liquid is cooled rapidly, it can form a glass, a state stuck between liquid and solid. Two groups looked in detail into analogous dynamics in electronic systems. Sato et al. and Sasaki et al. studied layered organic materials with a triangular in-plane lattice. These materials can assume a state in which their charge distribution has a regular pattern—an electronic or charge crystal. When the materials were cooled rapidly, a charge glass was formed instead and then allowed to crystallize. The dynamics of crystallization showed similarities to the analogous processes in conventional glasses. Science , this issue p. 1378 , p. 1381

The switching of electric polarization induced by electric fields -a fundamental functionality of ferroelectrics- is closely associated with the motions of the domain walls that separate regions with distinct polarization directions. Therefore, understanding domain-walls dynamics is of essential importance for advancing ferroelectric applications. In this Letter, we show that the topology of the multidomain structure can have an intrinsic impact on the degree of switchable polarization. Using a combination of polarization hysteresis measurements and piezoresponse force microscopy on a uniaxial organic ferroelectric, alpha-6,6'-dimethyl-2,2'-bipyridinium chloranilate, we found that the head-to-head (or tail-to-tail) charged domain walls are strongly pinned and thus impede the switching process; in contrast, if the charged domain walls are replaced with electrically neutral antiparallel domain walls, bulk polarization switching is achieved. Our findings suggest that manipulation of the multidomain topology can potentially control the switchable polarization., 17 pages, 5 figures

In this study we have investigated dopant effects on a typical charge-orbital ordered state in a single layered manganite La0.5Sr1.5MnO4 using magnetization measurement and resonant x-ray scattering technique. We have studied how the charge-orbital ordered state is affected by the 3% substitution of Cr, Fe and Ga ions for Mn ions. It is revealed that the impurity doping suppresses the long-range charge-orbital order, in which the degree of suppression strongly depends on dopant ions, and eventually forms a phase-separated ground state between charge-orbital order and ferromagnetic states.

We have prepared polycrystalline samples of the trimer Ir oxide BaIrO3 with face-shared Ir3O12 trimers, and have investigated the origin of the phase transition at 182 K by measuring resistivity, thermopower, magnetization and synchrotron x-ray diffraction. We propose a possible electronic model and transition mechanism, starting from a localized electron picture on the basis of the Rietveld refinement. Within this model, BaIrO3 can be basically regarded as a Mott insulator, when the Ir3O12 trimer is identified to one pseudo-atom or one lattice site. The transition can be viewed as a transition from the Mott insulator phase to a kind of charge ordered insulator phase., Comment: 8 pages 5 figures, Crystals (in press)

We have investigated the lattice distortion coupled to the Co $3d$-spin-state ordering in thin films of perovskite ${\mathrm{LaCoO}}_{3}$ with various epitaxial strains by measurements of the magnetization, x-ray diffraction, and optical spectra. In the system with tensile strain about 0.5%, a lattice distortion characterized by the modulation vector $q=(1/6,1/6,1/6)$ emerges at 40 K, followed by a ferromagnetic ordering at 24 K. Alternatively, in systems with tensile strain exceeding 1%, the lattice distortion characterized by $q=(1/4,1/4,1/4)$ emerges at 120 K or higher, and subsequently the ferromagnetic or ferrimagnetic ordering occurs around 90 K. The evolution of infrared phonon spectra and resonant x-ray scattering at the Co $K$ edge suggests that the population change in the Co $3d$ spin state causes the strain-induced switching of spin-state ordering as well as of magnetic ordering in this canonical spin-state crossover system.

Magnetic structure on SrMnO3 films has been investigated utilizing neutron magnetic scattering technique. We have succeeded in detecting a magnetic signal at (0.5 0.5 0.5) associated with G-type antiferromagnetic order. The temperature dependence of the signal intensity indicates a second-order transition with the transition temperature, T N ~ 190 K . This is a first step of our study of the magnetism in the manganite thin film system.

The crystal structure of BaFe2S3 is determined up to ~12 GPa by means of x-ray powder diffraction experiments using synchrotron radiation at room temperature. BaFe2S3 is the first superconductor in iron-based ladder compounds, showing the critical temperature at T c = 24 K under 11.6 GPa. The superconductivity emerges on the application of pressure after suppressing an antiferromagnetic Mott insulating state. The atomic positions in the superconducting state remain hitherto unknown experimentally. We found significant changes of structural parameters: shrinkage of the Fe-ladder unit and decreasing height of the S atom position from the Fe plane. Moreover, a reduction of the S–S distance between the ladders was observed under pressure. The pressure dependence of the structural parameters is strikingly different from the prediction of the band calculation.

Carbon brushes for automotive starters are used under severe conditions of high electrical current density, high contact pressure and high sliding velocity. Lead has traditionally been added to carbon brushes to improve their performance and durability. Because lead is an environmental hazardous substance, after January 2005 the EU has prohibited adding lead to carbon brushes for electric motors installed in new vehicles. This paper reports the development of the lead-free brush material for the high-load starter. Those brushes are used in much more extreme conditions - at a PV-value (the product of brush contact pressure and sliding velocity) approximately three times that of other starter brushes, and double the electrical current density. The major technical requirement of this development was to decrease the electrical wear in brushes caused by commutation sparking. We developed the brush material that reduces electrical wear by adding a phosphorous compound. Because the phosphorous compound can improve the lubricity at high-temperature and the contact stability of brushes, the developed brush reduces commutation sparks. The life of the developed brush is about 1.5 times longer than that of conventional brushes containing lead.

Resonant X-ray scattering (RXS) has been developed as a powerful technique to observe the orbital ordering in correlated electron systems. However, the scattering mechanism has been controversial, especially in K -absorption edge resonance of transition metal oxides. We have made it clear by measuring the interference terms between the resonant scattering term and the Thomson scattering term, or between the resonant terms of dipolar ( E 1) and quadrupolar ( E 2) transition processes. The results indicate that the Jahn–Teller mechanism is more responsible than the Coulomb mechanism in an e g electron system (La 0.5 Sr 0.5 MnO 3 thin films) of 3d transition metal oxide, but it is the opposite way in a t 2g electron system (YTiO 3 ) of 3d transition metal oxides and a 4f electron system (DyB 2 C 2 ).

Gd${}_{1-x}$Tb${}_{x}$MnO${}_{3}$ oxides are characterized by two main competing states that exhibit both ferroelectric and multiferroic ordering. Both states involve cycloidal magnetic order that drives ferroelectricity. In their new article, a collaboration of researchers from Japan discovered that exposure of Gd${}_{0.5}$Tb${}_{0.5}$MnO${}_{3}$ to x-ray irradiation induces a reversible transition into a new hidden state, which is also characterized by cycloidal order, but with a different modulation wave vector. The ability to manipulate the state with x-rays suggests a novel route for photocontrol of multiferroic materials.

We studied the Co valences and spin states in electron-doped LaCo$_{1-y}$Te$_{y}$O$_3$ by measuring x-ray absorption spectra and electron spin resonance. The low-temperature insulating state involves the low-spin Co$^{3+}$ ($S=0$) and the high-spin Co$^{2+}$ state, which is described by $g=3.8$ and $j_{\rm eff}=1/2$. The results, in concurrence with the electron-hole asymmetry confirmed in electrical resistivity, coincide with a spin-blockade phenomenon in this system. Further, we discuss the $g$ factor in terms of the strong covalent-bonding nature and consider multiple origins of this phenomenon., 7 pages, 5 figures, and 1 table

A synchrotron x-ray diffraction study of metal-insulator transitions in W-doped ${\text{VO}}_{2} ({\text{V}}_{1\ensuremath{-}x}{\text{W}}_{x}{\text{O}}_{2})$ thin films has been carried out. The insulating phase for $x\ensuremath{\le}0.07$ exhibits cell-doubling with the V dimerization similar to bulk ${\text{VO}}_{2}$, while the insulating phase for $x\ensuremath{\ge}0.11$ does not. This result suggests that the electronic structure of the $x\ensuremath{\ge}0.11$ insulators should be different from that of the $x\ensuremath{\le}0.07$ ones and bulk-insulating phase of ${\text{VO}}_{2}$. The temperature and $x$ dependence of superlattice reflection as observed casts doubt about the direct relationship between the dimerization of V ions and metal-insulator transition. The temperature dependence of the electrical resistivity rather implies the Mott-Anderson localization nature of the insulating phases. X-ray-induced persistent phase transitions are observed at low temperatures in each insulating phase in the vicinity of the boundary to the metallic phase regardless of the difference in the electronic structure. Gradual peak shift suggests that the x-ray irradiation produces nanometer metallic regions.

We have studied the orbitally ordered states in Y 1- x Ca x TiO 3 (0 < x ≤0.75) by resonant X-ray scattering (RXS) near the Ti K -edge ( E ∼5 keV) and by powder X-ray diffraction measurements. The ...

Carbon brushes for starters are used under severe conditions of high electric current density, high contact pressure and high, sliding velocity. Lead has traditionally been added to carbon brushes to improve their performance and durability. Because lead is an environmentally hazardous substance, after January 2005 the EU will prohibit adding lead to carbon brushes for electric motors installed in vehicles. The purpose of our current study is to develop materials of leas carton brushes for Starters. Analyzing the effects of adding lead has shown that lead inhibits the brush resistance from increasing under high temperatures, or a combination of both high temperature and high humidity. This is because corrosion of lead precedes that of copper. which is one of the materials comprising the brush, and this prevents the copper from corroding, Moreover, lead functions as a solid lubricant and reduces brush wear, We developed the lead-free brush material, by adding soft metallic substances that corrode prior to copper and are also oxidation-resistant, as well as possessing low hardness and solid lubricant properties. The developed lead-free brush surpasses the conventional lead-added brush in durability and permanence.

Orbitally ordered states of a Ti t 2 g -electron in Y 1- x Ca x TiO 3 (0 < x ≤0.5) have been systematically investigated by the resonant X-ray scattering (RXS) technique near the Ti K -edge. The RXS intensities at 1 s →3 d transition energy (pre-edge) reflecting the 3 d -orbital ordering markedly decrease with increasing Ca concentration toward the ferromagnetic–paramagnetic phase boundary ( x FP ∼0.15). The intensity remaining above x FP decreases gradually and almost disappears at the metal–insulator transition ( x MI ∼0.4). Namely, it is suggested that the orbital ordering is strongly suppressed toward x FP , and vanishes at x MI . The Ca concentration dependence of the Jahn–Teller distortion determined by X-ray structural analysis is consistent with the orbital state obtained by the RXS experiment.

Recently automotive fuel pumps installed in the fuel tank are still striving to increase the demands for high efficiency and high quality assurance. And as automotive supply continues to become increasingly global, the pumps have been used under various inferior gasoline containing higher sulfur concentrations in developing markets as compared with in general industrialized markets. Traditionally bronze alloy of Cu-Sn-C system is mainly used for the typical bearing of fuel pump applications. However it is very difficult to improve remarkably on the tribological performances of the demands for higher efficiency and so on. And what is more, the relatively high sulfur and sulfide contents gasoline is easy to cause sulfuration corrosion.In order to obtain excellent tribological performances and superior resistive to sulfuration, various copper based alloy of sintered bearings are investigated by powder metallurgy method. As a result, nickel silver alloy of Cu-Ni-Zn-C system shows both superior resistive to sulfuration and excellent tribological performance under the relatively high sulfur contents gasoline lubrication.

We developed an automatic feedback control system of the crystal–melt interface position to keep the temperature at the interface constant during growth, and demonstrate its successful application to grow Ge-rich SiGe bulk crystals with uniform composition. In this system, the position of the crystal–melt interface was automatically detected by analyzing the images captured using in situ monitoring system based on charge-coupled-devices camera, and the pulling rate of the crucible was corrected at every 1 min. The system was found to be effective to keep the crystal–melt interface position during growth even when the variation of the growth rate is quite large. Especially, the interface position was kept for 470 h during growth of Ge-rich SiGe bulk crystal when we started with a long growth melt of 80 mm. As a result, a 23 mm-long Si 0.22 Ge 0.78 bulk crystal with uniform composition was obtained thanks to the constancy of the growth temperature during growth through the control of the interface position. Our technique opens a possibility to put multicomponent bulk crystal in a practical use.

Charge and orbital ordering behaviors in the half doped bi-layered compound LaSr2Mn2O7 have been studied by resonant and non-resonant X-ray scattering. Three different order parameters, which correspond to the A-type antiferromagnetic, a charge and an orbital ordered states, were observed by measuring the magnetostriction and the superlattice peaks characterized by wavevectors (1/2 1/2 0) and (1/4 1/4 0), respectively. The superlattice reflections indicating the charge and orbital ordered states were observed below 210 K. Both the intensities reach a maximum at 160 K on cooling and become very weak below 100 K. The peak width of the charge ordered state agrees with that of the orbital ordered state at all temperatures studied. These results indicate that both the states originate from a single phase and that the charge/orbital ordered islands with definite interfaces disperse in the A-type antiferromagnetic phase. The dimensionality of the charge/orbital ordered phase is discussed using this model., 9pages, 10 figures

The electronic states in LaCo1−xRhxO3 have been investigated using X-ray absorption spectroscopy (XAS) to elucidate the Rh substitution effect on the Co spin state. The absorption spectra at the Co...

We have prepared polycrystalline samples of LaSrRh$_{1-x}$Ga$_x$O$_4$ and LaSr$_{1-x}$Ca$_x$RhO$_4$,and have measured the x-ray diffraction, resistivity, Seebeck coefficient, magnetization and electron spin resonance in order to evaluate their electronic states. The energy gap evaluated from the resistivity and the Seebeck coefficient systematically changes with the Ga concentration, and suggests that the system changes from a small polaron insulator to a band insulator. We find that all the samples show Curie-Weiss-like susceptibility with a small Weiss temperature of the order of 1 K, which is seriously incompatible with the collective wisdom that a trivalent rhodium ion is nonmagnetic. We have determined the $g$ factor to be $g$=2.3 from the electron spin resonance, and the spin number to be $S$=1 from the magnetization-field curves by fitting with a modified Brillouin function. The fraction of the $S$=1 spins is 2--5%, which depends on the degree of disorder in the La/Sr/Ca-site, which implies that disorder near the apical oxygen is related to the magnetism of this system. A possible origin for the magnetic Rh$^{3+}$ ions is discussed., 7 pages, 9 figures, Phys. Rev. B (accepted)

The critical cooling rate $R_{\rm c}$ above which charge ordering is kinetically avoided upon cooling, which results in charge-glass formation, was investigated for the geometrically frustrated system $\theta$-(BEDT-TTF)$_2X$. X-ray diffraction experiments revealed that $\theta$-(BEDT-TTF)$_2$TlCo(SCN)$_4$ exhibits a horizontally charge-ordered state, and kinetic avoidance of this state requires rapid cooling of faster than 150 K/min. This value is markedly higher than that reported for two other isostructural $\theta$-type compounds, thus demonstrating the lower charge-glass-forming ability of $X$ $=$ TlCo(SCN)$_4$. In accounting for the systematic variations of $R_{\rm c}$ among the three $\theta$-(BEDT-TTF)$_2X$, we found that stronger charge frustration leads to superior charge-glass former. Our results suggest that charge frustration tends to slow the kinetics of charge ordering., Comment: 4 pages, 3 figures. Selected for Editors' Choice

Non-equilibrium charge dynamics, such as cooling-rate-dependent charge vitrification and physical aging, have been demonstrated for a charge-cluster glass in $\theta$-(BEDT-TTF)$_2$CsZn(SCN)$_4$ using electron transport measurements. The temperature evolution of the relaxation time obeys the Arrhenius law, indicating that the glass-forming charge liquid can be classified as a "`strong" liquid in the scheme of canonical structural-glass formers. X-ray diffuse scattering further reveals that the spatial growth of charge clusters in the charge liquid is frozen below the glass transition temperature, indicating an intrinsic relationship between dynamics and structure in the charge-cluster glass., Comment: 5 pages, 5 figures

Hole concentration dependence of charge order (CO) and orbital order (OO) in layered perovskite compounds La 1- x Sr 1+ x MnO 4 has been studied by means of the resonant X-ray scattering technique. Both CO and OO are observed below 210 K in the compounds having the hole concentration x between 0.5 and 0.48, but neither is observed for x ≤0.46. The transition temperatures are nearly independent of x between 0.5 and 0.48. Correlation lengths ξ's for both orders obtained from analyses of superlattice peak profiles are finite at any temperature. Moreover, in contrast to the cubic perovskite, ξ for OO is larger than that for CO. ξ for OO is as short as that for CO at the critical concentration of x =0.48. These results suggest that OO is prerequisite to the forming of CO in this system.

A SiGe bulk crystal with uniform composition was successfully fabricated by clarifying and controlling the growth parameters at the crystal–melt interface. An apparatus was developed for the direct in situ observation and precise control of the interface parameters such as the temperature and the position. The dynamical change of the growth rate of a SiGe bulk crystal in a temperature gradient can be known by utilizing the apparatus. The growing crystal was continuously pulled down at the pulling rate balanced to the growth rate to keep the interface temperature constant, which resulted in the excellent uniformity of the grown crystal. Our technique opened the possibility to incorporate multicomponent semiconductor substrates to the semiconductor heterostructure technology.

Pressure effect on phase transition in NaV 2 O 5 has been studied at low temperature by x-ray scattering. In addition to two well-known phases at ambient pressure such as P-phase ( a × b × c orthorhombic unit cell at T > T c 0 = 35 K) and C\(_{\frac{1}{4}}\)-phase (2 a ×2 b ×4 c supercell at T < T c 0 ), we discovered a new high-pressure phase C 0 -phase, which has a 2 a ×2 b ×1 c supercell and is considered to be a new ground state above 0.92 GPa at T

The structural and magnetic properties of potassium-loaded zeolite LTA, K x -K 12 Si 12 Al 12 O 48 , were studied as a function of the loading density, x , up to ∼7. We observed a superlattice that develops with increasing loading density, and which is correlated with the low-temperature ( T ) magnetic phases. It was found that the ferromagnetic-like moment appearing at low T 's coexists with lattice modulations such as the mass density wave or the charge density wave.

Transmission electron microscope (TEM) observation at room temperature of the low temperature phase of Ni2.14Mn0.86Ga shows stress-induced 5 periodicity modulation along a pseudo-[111] cubic zone axis. On cooling to 173 K, the periodicity changes to 7. In stress-free areas, a [001] zone axis with new lattice parameters for the tetragonal phase was observed. The new lattice parameters are smaller by a factor of √2 than the expected lattice parameters. A new model for the tetragonal compound Ni2MnGa and the non-stoichiometric phases was developed with the help of TEM data, X-ray powder diffraction measurements, and a computational simulation based on the X-ray powder diffraction patterns.