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The frontal and parietal bones form the major part of the calvarium and their primordia appear at the basolateral region of the head and grow apically. A spontaneous loss of Foxc1 function mutant mouse, congenital hydrocephalus (Foxc1(ch/ch)), results in congenital hydrocephalus accompanied by defects in the apical part of the skull vault. We found that during the initiation stage of apical growth of the frontal bone primordium in the Foxc1(ch/ch) mouse, the Runx2 expression domain extended only to the basal side and bone sialoprotein (Bsp) and N-cadherin expression domains appeared only in the basal region. Fluorescent dye (DiI) labeling of the frontal primordium by ex-utero surgery confirmed that apical extension of the frontal bone primordium of the mouse was severely retarded, while extension to the basal side underneath the brain was largely unaffected. Consistent with this observation, decreased cell proliferation activity was seen at the apical tip but not the basal tip of the frontal bone primordium as determined by double detection of Runx2 transcripts and BrdU incorporation. Furthermore, expression of the osteogenic-related genes Bmp4 and-7 was observed only in the basal part of the meninges during the initiation period of primordium growth. These results suggest that a loss of Foxc1 function affects skull bone formation of the apical region and that Bmp expression in the meninges might influence the growth of the calvarial bone primordium.

The high-pressure technique is a fundamental tool for realizing novel phase transitions, chemical reactions, and other exotic phenomena. Hydrogenation is one example of a high-pressure reaction; at high pressures of several gigapascals, hydrogen becomes chemically active and reacts with metals and alloys to form hydrides. This paper covers a high-pressure study of the hydrogenation process and the synthesis of hydrides using a cubic-type multi-anvil apparatus. The experimental details of a hydrogenation cell assembly, high-temperature and high-pressure generation, and an in situ observation technique are presented. These experiments are conducted with the aid of in situ synchrotron radiation X-ray diffraction measurements operated in an energy-dispersive mode in the conventional manner for time-resolved measurements and a newly developed angle-dispersive mode for observation of the crystal growth process during formation of metal hydrides. Two successful cases of high-pressure hydrogenation are presented: aluminum hydride, AlH3, and an aluminum-based alloy hydride, Al2CuH x , which are potential candidates for hydrogen storage materials.

The effect of the vanadium content on the cyclic stability of V–Ti binary alloys was investigated. V 1− x Ti x , x = 0.2 and 0.5 samples were hydrogenated and dehydrogenated at 410 K and 553 K respectively, for more than 100 times. During hydrogen cycling, reduction in the reversible hydrogen storage capacity was clearly observed from both samples. No prominent V-effect was found. In fact, the reduction rates of two samples were similar; both samples showed a ∼25% reduction in the reversible hydrogen storage capacity after 100 cycles. In addition, the shape of the pressure–composition-isotherm (PCT) curves was significantly altered over the testing cycle period; the absorption and desorption plateaus got markedly inclined and the hysteresis became evidently smaller. We found that even after the hydrogen storage capacity of V 1− x Ti x was significantly reduced, at low enough temperature V 1− x Ti x was able to absorb hydrogen as much as it did at the first cycle. Furthermore, the reversible hydrogen storage capacity of V 0.8 Ti 0.2 at 410 K was recovered to a certain degree after hydrogenating the sample at low temperatures.

A long cycle life of metal hydrides is paramount for applications. We present an investigation of the degradation mechanism against hydrogenation cycles in Mg2–xPrxNi4 (x = 0.6 and 1.0). Mg1.0Pr1.0Ni4 shows significant degradation and loss of capacity after only a few cycles. In stark contrast, Mg1.4Pr0.6Ni4 did not show any reduction of hydrogen storage capacity until 100 cycles at 313 K. The peak broadening of X-ray diffraction (XRD) patterns and accumulation of lattice strain were observed concomitantly with an increase of hydrogenation cycles only in Mg1.0Pr1.0Ni4. These changes were not observed in Mg1.4Pr0.6Ni4. In pair distribution function (PDF) patterns, r-dependent peak broadening was observed and it became significant with an increasing number of cycles in Mg1.0Pr1.0Ni4, suggesting an increase of the dislocation density. Mg1.4Pr0.6Ni4 showed higher hardness and more pulverization upon hydrogenation than Mg1.0Pr1.0Ni4. These results suggest that the dominant mechanism, the stress induced by hydr...

ケイ酸カルシウムハイドレート（C-S-H）の構造と変形特性は、セメント化学における主な興味の対象であるが、完全には研究がなされていない。本研究では、53年前の完全水和ケイ酸三カルシウム（C3S）に対して、外部荷重下でC-S-Hの原子レベルでの構造変形を調べるため原子二体分布関数関数（PDF）解析を実施した。 C-S-Hの機械的特性に及ぼす老化の影響を解明するために、以前に実施した131日前のC3Sペーストに関するPDF解析結果との比較も行った。53年前のC3Sペーストは、131前のものよりも全体的な弾性率が高く、圧縮応力に対する耐性が優れていました。さらに、53年前のC3Sペーストのマクロなひずみは、マクロスケールでのマイクロクラックなどの機械的変形によって引き起こされたと考えられる。結果は、初期および後期におけるC-S-Hの原子レベルおよびメソスケールでの機械的挙動について実験的な証拠を提供する。

We report the development of an apparatus for Bragg coherent X-ray diffraction imaging (Bragg-CDI) at BL22XU of SPring-8, and show some typical results of the three dimensional imaging of BaTiO3 fine particles obtained using the apparatus. We studied two types of sample—particles with cubic-like shapes, and particles rich in curved surfaces. The shapes and sizes of the particles were successfully reconstructed, and are approximately consistent with results from scanning electron microscope (SEM) measurements. Further, details of the internal structure and reverse surface of the particles was obtained, information which is not available from SEM measurements. Our technique can currently be used to study particles as small as around 100 nm in size. Bragg-CDI is a powerful technique for investigating nanosized crystalline particles, and will open the door to studying particles located within devices such as multi-layered ceramic capacitors, inaccessible by electron beam techniques.

We investigated the hydrogenation of the L12-type AlNi3 alloy at 3 GPa and 500 °C using in situ synchrotron radiation X-ray diffraction measurements. An isotropic lattice expansion was observed to have occurred owing to the hydrogenation, and a novel hydride (AlNi3Hx) was formed. Because of such isotropic lattice expansion, the hydrogen-occupied sites were the body-center sites of the L12 structure (Pm-3m). In this case, the hydrogen content was calculated to be x = 1.0, which is consistent with the experimental results. The AlNi3Hx hydride was stable under ambient conditions.

Reduction in reversible hydrogen storage capacity with increasing hydrogenation and dehydrogenation cycle number is observed in numerous hydrogen storage materials, but the mechanism behind this unfavorable change has not been elucidated yet. In this study, we have investigated the development of structural defects or disorders in V1–xTixH2, x = 0, 0.2, and 0.5, during the first 15 hydrogen absorption and desorption cycles using the atomic pair distribution function (PDF) analysis of synchrotron X-ray total scattering data to find out the possible structural origin of the poor cyclic stability of V1–xTix alloys. While pure vanadium shows no significant change in the PDF, alloy samples subject to several hydrogenation and dehydrogenation cycles display fast decaying of the PDF profile due to a progressive increase in the PDF peak width with increasing r. This r-dependent PDF peak broadening effect becomes stronger with cycle number. Molecular dynamics (MD) simulations demonstrated that dislocation defects ...

We investigated the hydrogenation of a binary TiFe alloy at 5 GPa and 600 °C by in situ synchrotron radiation X-ray diffraction measurements. After formation of a solid solution of hydrogen in TiFe, an order–disorder phase transition in the metal lattice of TiFe occurred, which yielded a BCC TiFe hydride. The unit cell volume of the BCC hydride increased by 21.0% after the hydrogenation reaction. The volume expansion was larger than that of a γ -hydride TiFeH 1.9 prepared by hydrogenation near ambient conditions.

We determined the phase diagram and the equation of state (EoS) of TiH 2 at high pressures up to 8.7 GPa and high temperatures up to 600 °C by in situ synchrotron radiation X-ray diffraction measurements. Compression induced strain inhibited the phase transition from the low-temperature bct phase to the high-temperature fcc phase, making the phase diagram difficult to determine. However, heating around 600 °C relieved the strain, and the phase boundary between the bct and fcc phases was elucidated. The phase transition temperature at ambient pressure increased from around room temperature to 200 °C at 8.7 GPa. The high temperature Birch–Murnaghan EoS was determined for the fcc phase. With the pressure derivative of the bulk modulus K ′ 0 = 4.0, the following parameters were obtained: ambient bulk modulus K 0 = 97.7 ± 0.2 GPa, ambient unit cell of the fcc phase V 0 = 88.57 ± 0.02 A 3 , temperature derivative of the bulk modulus at constant pressure (∂ K /∂ T ) P = −0.01 ± 0.02, and volumetric thermal expansivity α = a + bT with a = 2.62 ± 1.4 × 10 −5 and b = 5.5 ± 4.5 × 10 −8 . K 0 of fcc TiH 2 was close to those for pure Ti and bct TiH 2 reported in previous studies.

The novel complex hydride YLiFeH6 with the Fe–H complex anion ([FeH6]4−) was synthesized by hydrogenation of YFe2 together with additional Li. Li adjusts the original imbalanced charge between Y3+ and [FeH6]4− by donating an electron to convert into Li+ during the hydrogenation, resulting in the formation of the well charge-balanced state of Y3+Li+[FeH6]4−.

Elastic deformation behaviors of as-cast and annealed eutectic and hypoeutectic Zr–Cu–Al bulk metallic glasses (BMG) were investigated on a basis of different strain-scales, determined by X-ray scattering and the strain gauge. The microscopic strains determined by Direct-space method and Reciprocal-space method were compared with the macroscopic strain measured by the strain gauge, and the difference in the deformation mechanism between eutectic and hypoeutectic Zr–Cu–Al BMGs was investigated by their correlation. The eutectic Zr50Cu40Al10 BMG obtains more homogeneous microstructure by free-volume annihilation after annealing, improving a resistance to deformation but degrading ductility because of a decrease in the volume fraction of weakly-bonded regions with relatively high mobility. On the other hand, the as-cast hypoeutectic Zr60Cu30Al10 BMG originally has homogeneous microstructure but loses its structural and elastic homogeneities because of nanocluster formation after annealing. Such structural changes by annealing might develop unique mechanical properties showing no degradations of ductility and toughness for the structural-relaxed hypoeutectic Zr60Cu30Al10 BMGs.

Hydrogenation pressure-temperature conditions of A6061 alloys were investigated at ultra-high pressures. Hydrogenation of these alloys at 550℃ and above 6 GPa formed AlH3. This pressure was two orders of magnitude higher than the pressure where these alloys were used as hydrogen storage vessels for fuel cell vehicles. Thus, it was concluded that A6061 alloys were not hydrogenated at the pressure-temperature conditions where hydrogen storage vessels were used.

The compressibility of lanthanum (La) metal and its hydrides were measured at room temperature by high pressure synchrotron X-ray diffraction. La metal pressurized in a hydrogen medium forms a hydride with an fcc metal lattice, which likely contains hydrogen at a concentration close to 3.0 and persists over the measured pressure span up to 21 GPa. Equations of state have been determined by helium compression experiments for LaH2 with tetrahedral interstitial sites fully occupied with hydrogen atoms and for LaH2.46 with octahedral interstitial sites partially occupied with hydrogen atoms and tetrahedral sites fully occupied. Both hydrides possess fcc metal lattices. The bulk modulus values B 0 are 66.7 ± 1.2 GPa for LaH2 and 68.4±1.0 GPa for LaH2.46. These values are three times larger than that of La metal and are very close to each other despite the difference in hydrogen occupation states. The hardening of the metal lattice by hydrogenation is attributed predominantly to hydrogen–metal interactions at the tetrahedral sites and is most pronounced for La, which has the largest ionic radius among rare-earth metals.

We present the first successful in situ simultaneous measurement of the electrical resistance and X-ray diffraction of FeH x (x∼ 1) under high-pressure H2 up to 25.5 GPa and low temperatures down to 9 K. The electrical resistivity ρ showed a sharp increase with the formation of iron-hydride FeH x (x∼ 1) at 3.5 GPa. The ϵ′-phase of FeH x was found to be metallic up to 25.5 GPa. The ρ vs. T curves up to 16.5 GPa approximately follow Fermi-liquid law below 25 K. However, T 5 was found to be better fitting at 25.5 GPa. This change can be considered to be related to the previously reported ferromagnetism collapse at corresponding pressure.

Raman and visible absorption spectra of rare earth trihydrides have been measured at high pressures, in order to investigate the structural and electronic phase transitions. The successive phase transitions of hcp-intermediate-fcc phase were confirmed by Raman measurements. From the visible absorption experiments, the band gap energy was estimated. The gap closure was found to occur on the transition from the intermediate to the fcc phase.

We present the newly developed electrical resistance measurement technique for metal hydrides compressed in high-pressure H2 and the first successful in-situ simultaneous measurements of electrical resistance and X-ray diffraction of FeH at high pressures and low temperatures. The electrical resistivity ρ showed a sharp increase with the formation of iron-hydride FeHx (x∼1) at 3.5 GPa. The e′-phase of FeH was found to be metallic up to 25.5 GPa. The ρ vs. T curves up to 16.5 GPa approximately follow Fermi-liquid law below 25 K. However, T5 was found to be better fitting at 25.5 GPa. This change can be related to the previously reported ferromagnetism collapse at corresponding pressures.

Negative thermal expansion (NTE) induced by intermetallic charge transfer between Bi5+ and Ni2+ was observed in Bi1− x Sb x NiO3 (x = 0.05 and 0.10). Bi3+ and Bi5+ had a long-range ordering in the low-temperature phase of Bi0.95Sb0.05NiO3 while the ordering was short-range in Bi0.9Sb0.1NiO3. The latter compound exhibited a continuous NTE with a linear coefficient of thermal expansion (CTE) of αL = −106 ppm K−1 without temperature hysteresis in a wide temperature range of 200–320 K.

The hydrogenation process of aluminum is observed at high pressure and temperature by angle-dispersive in situ X-ray diffraction method. At 10 GPa and 600 °C, single crystals of AlH3 about 20 μm in size are found to grow through three steps: self-pulverization of aluminum, hydrogenation of pulverized aluminum, and solid-state grain growth of hydride. The self-pulverization seems to be the precursor of the hydrogenation reaction because it occurs at pressure temperature conditions where AlH3 is thermodynamically stable.

Advanced Fundamental Research on Hydrogen Storage Materials (HYDRO☆STAR), was launched in 2007 to investigate the fundamental properties of hydrogen storage materials. The interest is focused on basic understanding of the hydrogen-metal interactions in metal hydride systems. Neutron scattering technique, which is capable of determining hydrogen positions and bonding states, is a key tool to investigate the interactions, and becomes significantly powerful when combined with high pressure technique, which realizes high hydrogen density states by compression of metal lattices. In this article, we present high-pressure neutron scattering techniques using Paris-Edinburgh cell and hydrogen-gas cell under development at J-PARC and JRR-3.

Pressure-induced structural transition of rare-earth metal hydride, YH3, has been investigated by synchrotron radiation X-ray diffraction experiments. We observed the pressure-induced structural transformation from the hexagonal metal lattice into an fcc one through an intermediate state, which appears in the wide pressure span of 12∼22 GPa. The obtained X-ray diffraction patterns in the intermediate state are represented by long-period structures, e.g. 27R, of the yttrium metal lattice. These long-period structures are interpreted in terms of the periodic arrangements of hexagonal-type and fcc-type stacking layers of the yttrium metals. Such structural transition is considered to be characteristic for rare-earth metal hydride.

The highly compressed state of metal hydride has been investigated to explore structural and electronic transitions characteristic to hydride. The hydrogen atoms play the lead in the transitions, showing displacement in or transfer between the interstitial sites of a metal lattice. One example is the band gap closing observed for a long period lattice of yttrium tri-hydride, YH3, appearing at pressures above 12 GPa. Another example is photochromic event observed again for yttrium hydride, YHx. The former is likely accompanied by the in-site displacement of hydrogen atoms and the latter by the site-to-site transfer.

We synthesized scandium hydrides by hydrogenation of a scandium foil with hydrogen fluid under high pressure at ambient temperature. Scandium dihydride (ScH 2 ) and trihydride (ScH 3 ) were prepared near 4 and 5 GPa, respectively. The hydrogenation process and pressure-induced structural changes in ScH 3 were investigated by synchrotron radiation X-ray diffraction measurements up to 54.7 GPa. A structural transition from hexagonal to the fcc lattice began at 30 GPa and was completed at 46 GPa via an intermediate state similar to those reported for other hexagonal trihydrides. The intermediate state was not interpreted in terms of a coexisting state for the low-pressure hexagonal and the high-pressure fcc structures. The onset transition pressure of ScH 3 supported the previously proposed relation that the hexagonal–fcc transition pressure is inversely proportional to the ionic radius of the trihydride.

We constructed a single-crystal synchrotron X-ray diffraction system to precisely study the structure under hydrostatic pressure conditions at low temperatures and applied it to a study on the phase transition phenomena of a Cd–Yb periodic approximant and a Cd–Yb quasicrystal. Four phases were newly observed for the 1/1 approximant crystal in a P–T range up to 5.2 GPa and down to 10 K. The innermost part of the atomic clusters of Cd4 tetrahedra exhibited various orientational ordering sensitively depending on pressure and temperature. High pressure diffraction measurements using a highly parallel synchrotron X-ray beam and a hydrostatically compressed single crystal enabled us to detect the weak diffractions due to the subtle structural changes.

A metal to insulator transition in integer or half integer charge systems can be regarded as crystallization of charges. The insulating state tends to have a glassy nature when randomness or geometrical frustration exists. We report that the charge glass state is realized in a perovskite compound PbCrO3, which has been known for almost 50 years, without any obvious inhomogeneity or triangular arrangement in the charge system. PbCrO3 has a valence state of Pb(2+)(0.5)Pb(4+)(0.5)Cr(3+)O3 with Pb(2+)-Pb(4+) correlation length of three lattice-spacings at ambient condition. A pressure induced melting of charge glass and simultaneous Pb-Cr charge transfer causes an insulator to metal transition and ∼10% volume collapse.

The title compound is synthesized from a mixture of Bi2O3, ZnO, V2O3, and V2O5 with 10% excess of Bi and Zn (gold capsule, 9 GPa, 1373 K, 30 min).

Pressure induced structural transition of yttrium hydride has been investigated using synchrotron radiation X-ray diffraction measurement up to 24 GPa at room temperature. A reversible hexagonal–fcc transition with a wide intermediate region from 11 to 20 GPa is confirmed, which is consistent with previously reported X-ray results. The diffraction patterns measured for the intermediate state are not interpreted in terms of a hexagonal–fcc coexisting state or as rare-earth structures with various metal-layer stacking sequences. The equation of state determined for the hexagonal–YH 3 provides a bulk modulus B 0 of 71.9 GPa, which is nearly half of the previously reported value, but is within the range of values reported for other rare-earth metal trihydrides with hexagonal structures.

We have derived the magnetic phase diagram for Nd 1/2 Ca 1/2 (Mn 1- y M y )O 3 ( M = Ru, Cr and Sc) based on the neutron powder diffraction measurements. We found that the Ru- and Cr-doping induces an antiferromagnetic-to-ferromagnetic transition at y =0.01–0.02, while the Sc-doping does not induce the transition up to y =0.10. We have found significant dopant dependent effects on the distortion of the MnO 6 octahedra in the heavily-doped region of the long- c phase: the MnO 6 shape approached to the 2-long/4-short type with Ru-doping, while it does to the 4-long/2-short type with Sc-doping. Absence of the ferromagnetic phase in the Sc-doped system can be ascribed to (1) a strong charge-ordering instability due to the 4-long/2-short type distortion of the MnO 6 octahedra and (2) the reduced effective one-electron bandwidth due to the Sc 3+ ( d 0 ) impurities.

Lattice and magnetic properties are investigated for 3% Ru- and Cr-doped Nd 1/2 Ca 1/2 MnO 3 . The parent Nd 1/2 Ca 1/2 MnO 3 is a charge-ordered insulator ( T CO = 250 K). With decreasing temperature below ≈ 210 K, these compounds are separated into two perovskite phases, that is, the long- c and short- c phases. The long- c region shows a ferromagnetic transition at T C ≈210 K for the Ru-doped compound and ≈ 130 K for the Cr-doped compound, while the short- c region shows antiferromagnetic transition at T N ≈150 K for Ru and ≈ 110 K for Cr. We discuss the origin of the enhanced T C for the Ru-doped compound in terms of the effective one-electron bandwidth W of the e g -band.

Photoinduced effects in a La 0.6 Sr 0.4 MnO 3 film ( T c ∼315 K) have been investigated in the temperature range 290–470 K by means of a pump-probe method. Below T c , we have observed transient transmission changes Δ T / T induced by pump pulse excitations at 2.54 and 1.55 eV, which have been interpreted in terms of the photoinduced spin-disorder in the ferromagnetic phase. We further have compared the photoinduced Δ T / T with the photoinduced resistivity change Δ R / R .

Impurity effect on the charge and orbital ordered (CO/OO) state in doped manganites has been studied by the transmission electron microscopy (TEM), in addition to the electric and magnetic measurements. In the Cr-doped manganites (Nd 0.5 Ca 0.5 Mn 1- y Cr y O 3 ), the CO/OO state characterized by the incommensurate wave vector is still realized as the microdomains with the size of 10–30 nm even at lower temperature of 20 K. On the other hand, the Sc-doped manganites (Nd 0.5 Ca 0.5 Mn 1- y Sc y O 3 ) clearly show an incommensurate to commensurate structural phase transition accompanying the formation of the long-ranged CO/OO state around 60 K. From our experimental findings, it is suggested that the substituted Cr 3+ and Sc 3+ ions serve as the spin impurity and hole vacancy, respectively.

Microscopic magnetic structures of Tb 1- x Ca x MnO 3 ( x ∼1) have been investigated by means of small-angle neutron scattering (SANS) and Lorentz micrograph experiments. We have found that ferromagnetic microclusters of the order of ∼10 nm are invaded in the antiferromagnetic matrix with the G-type spin structure. We have interpreted the coexistence of the magnetic clusters in terms of intrinsic change separation.

The pressure-induced disproportionation reaction of LaH2 was investigated by infrared reflection and Raman measurements at ambient temperature. The relative reflection intensity in the 4000–6000 cm−1 region began to decrease significantly at a pressure of about 12 GPa and fell to 10% of the initial value at 20 GPa. Absorption peaks, which appeared around 1200 and 700 cm−1 at pressures above 14 GPa, were assigned to the hydrogen vibrations at the tetrahedral and octahedral sites of the fcc metal lattice, respectively. The peak frequencies measured in the 14–30 GPa range were similar to those observed in LaH3. These infrared results indicated insulating LaH3 precipitated from metallic LaH2. Above 20 GPa, a Raman peak related to the hydrogen vibration in the octahedral sites appeared around 700 cm−1, and was likely due to lattice distortion. The disproportionation reaction of LaH2 into LaH 2 + δ and solid solution LaHx ( x 1 ) was confirmed.

The hydrogenation process of aluminum, especially pulverization of aluminum prior to the hydrogenation reaction was investigated by in situ synchrotron radiation X-ray diffraction measurements at high pressure and high temperature. Changes in the crystal grain sizes during the hydrogenation process were observed using the angle dispersive method, while weak Bragg peaks from aluminum and AlH3 with small X-ray scattering factors were detected using focused monochromatic X-rays as the incident beam. The in situ measurement system monitored the pulverization of aluminum at several pressure-temperature conditions where AlH3 was thermodynamically stable.

An Al3Ti alloy was immersed in hydrogen at high pressures and high temperatures. An anomalous expansion of the Al3Ti metal lattice was observed by in situ powder X-ray diffraction measurements at 625°C and 10 GPa, suggesting that Al3Ti is hydrogenated to form Al3TiHx. The hydrogen content is roughly estimated to be x∼0.4. However, the formed hydride phase is dehydrogenated during depressurization, and cannot be recovered at ambient conditions.

Hydrogen composition and occupation state provide basic information for understanding various properties of the metal–hydrogen system, ranging from microscopic properties such as hydrogen diffusion to macroscopic properties such as phase stability. Here the deuterization process of face-centred cubic Fe to form solid-solution face-centred cubic FeDx is investigated using in situ neutron diffraction at high temperature and pressure. In a completely deuterized specimen at 988 K and 6.3 GPa, deuterium atoms occupy octahedral and tetrahedral interstitial sites with an occupancy of 0.532(9) and 0.056(5), respectively, giving a deuterium composition x of 0.64(1). During deuterization, the metal lattice expands approximately linearly with deuterium composition at a rate of 2.21 Å3 per deuterium atom. The minor occupation of the tetrahedral site is thermally driven by the intersite movement of deuterium atoms along the ‹111› direction in the face-centred cubic metal lattice., Knowledge of hydrogen content and coordination in deuterized metals is of importance. Here, the authors study the deuterization of face-centred cubic iron in-situ via neutron diffraction, observing the occupation by hydrogen of both octahedral and tetrahedral interstitial sites.

Crystal and magnetic structures of Tb 1- x Ca x MnO 3 ( x ≥0.5) have been investigated by means of neutron powder diffraction experiments. We have derived the magnetic phase diagram against hole concentration x and temperature T : the spin structure changes as CE- → C- → G-type structure with increase of x . In the vicinity of the magnetic phase boundaries, magnetically phase separated state has been observed. At high temperature region, we observe the metallic behavior in a wide x region (0.70 ≤ x ≤0.95), and ascribe it to the enhanced one-electron bandwidth W of the e g state.

Temperature variation of the crystal structure has been investigated for Tb 2 Ba 2 Co 4 O 11 , which shows a metal-insulator (MI) transition at T MI = 340 K. The compound has a layered-type double-perovskite structure along the c -axis, with alternating the CoO 6 octahedron and the CoO 5 pyramids along the a -axis. With decrease of temperature below T MI , the distortion of the octahedral and pyramidal sites is fairly released, suggesting that spin state transition of the Co 3+ ions is the origin for the MI transition.

We have found that spinel AlV 2 O 4 shows a phase transition at ∼700 K with anomalies of transport and magnetic properties. It is clarified that this corresponds to a charge-ordering transition, where the V 2.5+ ions are separated into three V 2.5-δ ions and one V 2.5+3δ ion. This three-one type of charge ordering, which is coupled with rhombohedral distortion along the (111) axis, reduces the high degeneracy of ground states inherent in this spinel structure, and thus can be understood in terms of “charge frustration.”

Destabilization of the charge-ordered (CO) state in half-doped manganites by chromium (Cr) doping in the manganese (Mn) sites was investigated. The Cr doping in the half-doped manganites makes the ...

Effects of the electron doping on the magnetic and electronic properties have been investigated in the conducting double perovskite ${\mathrm{Sr}}_{2}{\mathrm{FeMoO}}_{6}.$ Judging from the enhanced moment ${\ensuremath{\mu}}_{\mathrm{Mo}}$ at the Mo site, the doped electrons are considered to occupy mainly the down-spin $\mathrm{Mo}4d$ band. Filling dependence of the saturation magnetization ${M}_{\mathrm{s}},$ the spin-wave stiffness coefficient ${D}_{\mathrm{s}}$ and the $\ensuremath{\gamma}$ coefficient are discussed on the basis of a $\mathrm{LDA}+U$ band calculation. We further discuss possible origins for the magnetism.

Crystal and magnetic structures of Cr-doped manganites, Nd 1/2 Ca 1/2 Mn 1- y Cr y O 3 ( y =0.00 and 0.03), have been investigated by synchrotron radiation (SR) x-ray powder diffraction as well as neutron powder diffraction measurements. A detailed analysis of the high-resolution x-ray profile has revealed that the Cr-doped compound exhibits broad extra reflections, suggesting the formation of microdomains below the charge-ordering temperature T CO . The origin of the microdomain structure is discussed in terms of the charge separation.