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A graphite-like material boron carbide (BCx) was synthesized under various heat treatment conditions and extensively characterized. First, we synthesized the BCxprecursor phase by a single-step reaction using a mixed solution of BBr3and C6H6. We confirmed that the precursor phase had a graphite-like structure with B–C chemical bonds, but its crystallinity was poor. To improve their crystallinity, we annealed the precursor sample at high temperature using a high-frequency furnace and determined the annealing condition. We also investigated the magnetic properties of BCx. The high-temperature annealing for the precursor phase yields the highest Pauli paramagnetic susceptibility χPauli, indicating the highest density of states at the Fermi level. Accordingly, the high-temperature treatment for the precursor phase is significant to improve its crystallinity and physical properties. In addition, we synthesized a Ti-intercalated material TiBC by using the same procedure as that for making the BCxprecursor phase. The crystal structure can be indexed by the AlB2structure, indicating that Ti atoms are intercalated between the BC layers. The χPaulivalue of TiBC is obtained to be 1 order of magnitude smaller than that of BCx, suggesting the compensation of hole carriers by electron doping through Ti intercalation into the BCxsystem.

A new DRAM cell structure for 256-Mbit and 1-Gbit DRAMs has been developed in which the cell capacitors are flexibly formed like a stacked capacitor (STC), but are buried under […]

A new oxide, Bi(Mg1/2Ti1/2)O3 was prepared using a high-pressure high-temperature technique at 8 GPa and 1000ºC. As-sintered Bi(Mg1/2Ti1/2)O3 has the BiFeO3-type perovskite structure with the rhombohedral R3c. After ground, crystal structure changed to tetragonal P4mm. Structure parameters of tetragonal Bi(Mg1/2Ti1/2)O3 were refined from laboratory X-ray powder diffraction data (a = 4.033(10) Å, and c = 3.938(10) Å). Bi(Mg1/2Ti1/2)O3 does not decompress at ambient pressure, but the structure changed from rhombohedral to tetragonal on heating above 800°C. This phase transition was nonreversible. Bi(Mg1/2Ti1/2)O3 is expected to be one of the end members of lead-free ferroelectric materials.

Magnetic and dielectric properties of the ruthenium double perovskites La2MRuO6 (M = Mg, Co, Ni, and Zn) were investigated. The magnetization measurements for M = Co and Ni showed the existence of magnetic order at 20–30 K. Though the oxides with M = Zn and Mg exhibit a deviation from the Curie–Weiss law, magnetic order was not clearly observed. The result of La2ZnRuO6 was different from that previously reported, in which a ferromagnetic transition was found at around 165 K. The AC dielectric measurements for M = Co and Ni showed large dielectric constants (typically larger than 1000) at around room temperature, suggesting both the formation of short-ranged polar regions and the magnetic origin of large dielectric constant. In addition, two peaks were found for the temperature dependence of the tan δ component for La2NiRuO6. The behavior suggests the existence of two different polar regions. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

YFe 2 O 4 m i ( i < 0.005), which is a member of charge-frustrated system RFe 2 O 4 was synthesized and investigated by the low-temperature synchrotron powder X-ray diffraction. The structure between 225K and 250K is the same with the three-dimensional charge ordered state of LuFe 2 O 4 . Below the charge ordering temperature, at least five different phase transitions were detected. Since the balance of competing interaction between ionic charge essentially dominates the presence of multi phases in frustrated system, the low oxygen deficiency in YFe 2 O 4 m i is considered as the origin of the multi phases in low temperature.

We report a synchrotron orbital radiation study of a charge ordering in a triangular mixed valence system LuFe2O4. Using the X-ray anomalous dispersion method near the iron K-shell absorption edge, we confirmed a superstructure of Fe2+ and Fe3+ on the triangular lattice with a configuration of a √3 × √3 × 2 structure. This charge structure shows a spontaneous polarization.The existence of two dimensional charge ordering above 330K was deduced from the temperature dependence of the energy dispersion for the superlattice reflection.

We report a simple alternating current magnetometer. It is based on the principle of an ordinary Hartshorn bridge. The use of a two-channel oscillator allowed us a simple construction and a sensitivity of magnetic moment better than 10-6emu, normally sufficient for superconductivity studies. The whole system is controlled by a personal computer to collect the data automatically.

We report the magnetoelectric effect of a polycrystalline sample of a triangular Ising antiferromagnet ErFe2O4-δ, in which the existence of short range charge ordering was inferred from the neutron and dielectric studies. The sign of the magnetoelectric signal was reversed at 77 K, when the electric or magnetic field was applied in the opposite directions during cooling the specimen down to 77 K. The sign of the signal was independent of the direction of the static bias magnetic field in the range above 150 K. The signal was maximum at 183 K. We suggest a relation between the origin of the magnetoelectric effect and the dielectric relaxation due to an electron hopping between Fe3- and Fe2+ sites.

We report the change of the superconducting transition temperature Tc with the substitution of rare earth with cadmium in the RE1-xCdxBa2Cu3Oy system, where RE is Nd, Eu, Gd, Dy and Y. The decrease of Tc with the amount of Cd was found to be closely related to the radius of the RE3+ ion.

This study aims to analyze if managerial optimism affects corporate investment behavior. We measure managerial optimism by directly surveying CFOs and executives responsible for corporate investments of listed companies in Japan. We show that capital investment is higher when managers are optimistic. When we combine our survey data of Japanese managers with comparable cross-country data, we find that companies located in countries with highly optimistic managers invest more actively. This implies that managerial optimism not only partly explains differences of corporate behaviors in a country, but also those among countries.

α′‐NaV2O5transforms at TC= 34 K, and the origin of the phase transition seems to be caused by the charge order and spin‐Peierls mechanism. However the experiments which reveal the existence of charge order are very little. We measured XANES of V atoms which relates to the valence of V. It was found that the valences of V atoms in NaV2O5were V4.5+in the high temperature phase by comparing pre‐edge and XANES of NaV2O5with that of LiV$_2O5, CaV2O5and V2O5. The analysis of EXAFS also shows the environment of the V4.5+state.

Well-crystallized epitaxial YbFe2O4 films were prepared on an a-Al2O3(001) substrate using an Fe3O4 buffer layer. Fe3O4 has a relatively small lattice mismatch with both YbFe2O4 and a-Al2O3. Electron diffraction analysis combined with transmission electron microscopy revealed the epitaxial relationship to be a-Al2O3[110](001) [?] Fe3O4[$\bar{2}11$](111) [?] YbFe2O4[110](001). Moreover, superlattice spots due the Fe2+-Fe3+ charge order state of YbFe2O4 were clarified. The Fe2+/Fe3+ ratio in YbFe2O4 was nearly stoichiometric. The film exhibited a ferrimagnetic transition at [?]220 K and a nonlinear current-voltage characteristic at room temperature. These results confirmed the good crystallinity and stoichiometry of the obtained YbFe2O4 films.

An exchange bias (EB) behavior has been observed for multiferroic $R$Fe2O4($R=\text{Y}$, Er, Tm, Yb, Lu, and In). The materials with small $R^{3+}$ ions ($R=\text{Tm}$, Yb, Lu, and In) exhibit large EB fields (${\gtrsim}1$ kOe) below ${\sim}100{\mbox{--}}150$ K. This property is rooted in a magnetically glassy state, arising from the competition between ferromagnetic and antiferromagnetic domain interactions. In addition, the EB field tends to be more enhanced for smaller $R^{3+}$ ions. Hence, the EB is controlled by the substitution at the $R$-site in this series.

The coexistence of ferroelectricity and magnetic order in epitaxial hexagonal YbFeO3(h-YbFeO3) thin films deposited on yttria stabilized zirconia substrates is examined using an impedance analyzer, a second harmonic generation (SHG) microscope, an X-ray diffractometer, a transmission electron microscope and a superconducting quantum interference device magnetometer. The results show that h-YbFeO3films exhibit ferroelectricity below 350 K with threefold translational periodicity along the [110] direction similar to rare earth manganese oxides, and ferrimagnetism with a four-up and two-down spin configuration of Fe+3and Yb+3ions along the $c$-axis at low temperatures. In addition, a possibility of new ferroelectric phases with an electronic origin induced by the magnetic ordering is discussed based upon SHG and $D$--$E$ hysteresis measurements.

Simultaneous synchrotron radiation and transport measurements for the organic thyristor family compound $\theta$-(BEDT-TTF)2RbZn(SCN)4have revealed the presence of microscopic competing domains between the twofold and $3 \times 4$ charge orderings in a triangular lattice. In contrast to conventional correlated electron systems, charge ordering is a unique critical parameter of phase competition. With external current, only the twofold ordering melts, which is responsible for the emergence of a nonlinear response.

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Synchrotron x-ray measurements were done on the charge ordered state of La1-xSrxMnO3(x?0.12). In accordance with previous neutron diffraction study, super-lattice reflections which double the b-axis were observed. From the extinction rule of the super-lattice reflections, layer-type charge ordering pattern is plausible. Temperature dependence of the super-lattice peaks might indicate that a certain kind of competition exists in this system.

An improvement of a Hartshorn type alternating current magnetometer is reported. The use of a dual channel oscillator, a two-phase lock-in amplifier and a personal computer enabled us to obtain a simple feedback system for automatic balancing of the bridge. The resolution of this system is about 3×10-7emu of magnetic moment or higher at the field of 0.8 Oe in amplitude and 159 Hz in frequency.