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We have measured Ca-intercalated graphite superconductor CaC 6 (T c = = 11.2 K) by soft X-ray photoemission spectroscopy in order to understand the electronic structure. For the valence band, we observed several structures that correspond to those of calculated density of states with the partial density of states of Ca 3d at the Fermi level (E F ). We also observed core level spectra that are a very large asymmetric Ca 2p and asymmetric C 1s for CaC 6 , suggesting the existence of conduction electrons derived from Ca 3d and a charge transfer from Ca to graphene layer. These results provide spectroscopic evidence for PDOS of Ca 3d at E F . From a comparison of electronic structure of CaC 6 and other graphite intercalation compounds (GlCs), we found the difference between CaC 6 and other superconducting GlCs, which provides deeper understanding of the superconductivity of CaC 6 .

We have developed a miniature piston–cylinder pressure-cell for the measurement of specific heat by adiabatic method. It produces pressures up to 1.5 GPa and could be used in the temperature range 0.7–5 K. The pressure-cell is designed to be employed with a commercial Superconducting Quantum Interference Device (SQUID) magnetometer in order to enable to determine the exact value of applied pressure. We carried out calibration by measuring the pressure dependence of the mixture of the Fluorinert 70 and 77 which is a transmitting medium for the pressure-cell. We have also developed an automated sampling method for the specific heat measurement. To demonstrate the performance of the present measurement system, we have performed the specific heat measurements for CeRhSi3 up to 1.2 GPa. The results obtained have enough quality to discuss pressure dependence of the magnetic entropy and the magnetic phase transition.

We have developed the heat capacity measurement systems under high pressure for solid state materials by an adiabatic method and AC method. In this paper, it is discussed our measurement systems. For measurement of heat capacity by an adiabatic method, it was constructed the CuBe piston–cylinder type cell whose size is 8.8 ×2.7 ×21 mm in outer-diameter, inner-diameter and length, respectively. We show the results of specific heat under high pressure in CeRhSi 3 by using our cell. It is clearly seen the coexistence of the magnetic ordering and superconductivity under high pressure and low temperature. For measurement of heat capacity by an AC method by using another type of piston cylinder cell, we show the results for CePd 2 Si 2 . It also mentioned the possible measurement system by using a cubic anvil press.

A micro-pressure cell has been developed for measurements of specific heat and magnetization by using a commercial SQUID magnetometer. This small piston-cylinder device can be used up to 2 GPa. In this paper, we report on the efficiency of our micro-cell and present some results of the pressure effect on the magnetic and thermal properties of CeAg.

Tetragonal FeSe is a superconductor with a transition temperature Tc of 8 K and shows a huge enhancement of Tc with applying pressure. Tetragonal FeTe has a structure very analogous to superconducting FeSe, but does not show superconducting transition. We investigated the pressure effect of resistivity on FeTe. The resistivity at room temperature decreased with increasing pressure. An anomaly in resistivity around 80 K shifted towards a lower temperature with increasing pressure., Comment: 15 pages, 5 figures, ISS2008

We measured the heat capacity of CeIrSi 3 (100 mK T P =1.38 GPa. The measurements have been used a quasiadiabatic method utilizing a CuBe piston-cylinder pressure cell in a dilution refrigerator. At 0 GPa, a sharp anomaly which indicates the antiferromagnetically transition is observed at T N =5 K. T N decreases monotonically with increasing pressure up to P =1.38 GPa. The magnetic entropy is released below T N only 19% of R ln 2 at 0 GPa. And the magnetic entropy decreases with increasing pressure up to 1.38 GPa, 64% compared to that at 0 GPa.

The superconducting transition temperature of homoepitaxial boron-doped diamond thin films fabricated by microwave plasma-assisted chemical vapor deposition technique depend on substrate orientation. In addition, heavily doped diamond thin films indicate anisotropic lattice expansion. From these points of view, pressure effect will give us knowledge of the superconducting mechanism of boron-doped diamond. We report measurements of the electrical resistivity of heavily boron-doped diamond thin film under pressure up to P = 1.45 GPa and 1.27 GPa for (1 1 1) and (1 0 0) homoepitaxial thin films, respectively. The superconducting transition temperature decreases linearly with increasing pressure by a rate of δ T c /δ P = −1.17 × 10 −1 K/GPa and −1.51 × 10 −2 K/GPa for (1 1 1) and (1 0 0) thin film, respectively.

We report measurements of the heat capacity of pressure-induced superconductivity in an antiferromagnet CeRhSi 3 under pressure up to P = 1.34 GPa . CeRhSi 3 crystallizes into the tetragonal BaNiSn 3 -type structure without inversion center, which is the same as newly discovered superconductor CePt 3 Si . At ambient pressure a pronounced anomaly in the specific heat is observed, indicating the transition to an antiferromagnetically ordered state at T N = 1.61 K . T N increases with increasing pressure below around P = 0.75 GPa and then decrease with increasing pressure. At P = 1.34 GPa , we confirmed the superconductivity at T c = 0.45 K by the specific heat measurement, which was previously reported by the electrical resistivity measurement.

High dielectric capacitor, that has around 1000 in dielectric constant, can be successfully formed by nanotransfer on non-heat-resisting substrates. PZT film could be released from the Si substrate and bonded onto the polymer one. The releasing characteristics have the relationships with the thickness of Pt layer. The formed PZT has perovskite structure and clear columnar texture. The proposal of the structure of electrode using Ti is shown in case of the stress film

We investigated the pressure effects on the FeSe superconductor and the related compounds. Pressure dependence of superconducting transition temperature (Tc) for FeSe0.8S0.2 exhibits a dome-shaped behavior below 0.76 GPa. On the other hand, the Tc of FeSe0.25Te0.75 linearly increases up to 0.99 GPa. Here we discuss the relation between the physical pressure effects and the chemical pressure effects on the FeSe system., 8 pages, 5 figures, proceedings of the 2009 M2S conference

We have performed soft x-ray photoemission studies of Ca-intercalated graphite superconductor ${\text{CaC}}_{6}({T}_{\text{c}}=11.2\text{ }\text{K})$. The valence-band spectrum shows six main structures, with a peak at the Fermi level $({E}_{\text{F}})$, which correspond to those of calculated DOS. The intensity of the ${E}_{\text{F}}$ peak is resonantly enhanced at the $\text{Ca}\text{ }2p\text{\ensuremath{-}}3d$ threshold, providing spectroscopic evidence for the existence of $\text{Ca}\text{ }3d$ electrons at ${E}_{\text{F}}$, which is confirmed experimentally for the first time. The $\text{Ca}\text{ }2p$ core-level spectrum has a very large asymmetric line shape, which is further possible suggestion of the existence of $\text{Ca}\text{ }3d$ derived conduction electrons at Ca sites. These results strongly support the picture where $\text{Ca}\text{ }3d$ derived interlayer band plays a crucial role for the superconductivity of this material with relatively high ${T}_{\text{c}}$.

We have investigated the effect of atomic substitutions in the FeSe system, which exhibits the simplest crystal structure among the iron-based superconductors. An enhancement of the superconducting transition temperature Tc was observed with the substitution of S or Te for Se; the Tc increased with S substitution by up to 20 %, and also increased with Te substitution up to 75 %. In contrast, Co or Ni substitutions for the Fe site significantly suppressed superconductivity. In this work we present a detailed description of the substitution technique employed to determine Tc in the FeSe system., 17 pages, 15 figures, 1 table

Single-crystalline (Lu, Ca)Ba2Cu3O7-d (Lu(Ca)123) whiskers have been successfully grown using the Te-doping method. X-ray diffraction patterns of Lu(Ca)123 whiskers showed sharp (0 0 l) peaks corresponding to REBa2Cu3O7-d phase (RE = rare earth elements). Transport measurements showed that the superconducting transition occurred at 83 K in the obtained whiskers., Comment: 3 pages, 3 figures, ISS2008

A huge enhancement of the superconducting transition temperature Tc was observed in tetragonal FeSe superconductor under high pressure. The onset temperature became as high as 27 K at 1.48 GPa and the pressure coefficient showed a huge value of 9.1 K/GPa. The upper critical field Hc2 was estimated to be ~ 72 T at 1.48 GPa. Because of the high Hc2, FeSe system may be a candidate for application as superconducting wire rods. Moreover, the investigation of superconductivity on simple structured FeSe may provide important clues to the mechanism of superconductivity in iron-based superconductors., Comment: 8 pages, 6 figures

In this work, we have performed resonant photoemission studies of Ca-intercalated graphite superconductor CaC6. Using photon energy of the Ca 2p-3d threshold, the photoemission intensity of the peak at Fermi energy (E-F) is resonantly enhanced. This result provides spectroscopic evidence for the existence of Ca 3d states at E-F, and strongly supports that Ca 3d state plays a crucial role for the superconductivity of this material with relatively high T-c.

We have performed AC calorimetric measurement under high pressure up to 1.56 GPa using a Cu–Be and Ni–Cr–Al hybrid piston cylinder cell in the temperature range from 2 to 12 K in CePd 2 Si 2 . It is clearly seen magnetic ordering temperature T N and magnetic contribution are suppressed under high pressures.

We have fabricated a piston–cylinder cell for the measurements of specific heat and magnetization under high pressure up to 2 GPa. The sizes of CuBe cylinder are 8.8, 2.7 and 21 mm in outer-diameter, inner-diameter and length, respectively. ZrO 2 was used for the piston and the piston-backup. The magnetic properties and the specific heat under the action of the same pressure were measured by a commercial SQUID magnetometer and a standard adiabatic method.

The electrical resistance of an individual boron-doped multi-walled carbon nanotube was measured under high pressure up to 1.73 GPa. The resistance decreased drastically when pressure was applied. The temperature dependence of the resistance was explained by a variable range hopping transport model, and the dimensionality was observed to change from one to three dimensions with increasing pressure.

We have successfully synthesized a new superconducting phase of FeTe1-xSx with a PbO-type structure. It has the simplest crystal structure in iron-based superconductors. Superconducting transition temperature is about 10 K at x = 0.2. The upper critical field Hc2 was estimated to be ~70 T. The coherent length was calculated to be ~2.2 nm. Because FeTe1-xSx is composed of nontoxic elements, this material is a candidate for applications and will activate more and more research on iron-based superconductor., Comment: 13 pages, 10 figures