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Effects of pressure on the physical properties are very important for understanding highly correlated electron systems, in which pressure-induced attractive phenomena such as superconductivity and magnetically ordered non-Fermi liquid have been observed. Up to now, many scientists have developed a lot of high pressure apparatus for each purpose. In this paper, we present the very small “palm cubic-anvil high-pressure apparatus” for precise electric transport measurements under high pressure up to 8 GPa. The most outstanding characteristic of this pressure cell is its compactness. This cell enables us to measure absolute values of electrical resistivity, magneto-resistance and Hall coefficient at various temperatures. The details of our palm cubic high-pressure apparatus are introduced, and some neutron experimental results at room temperature are discussed.

In this article, various materials used for the fabrication of high-pressure apparatus are reviewed. Stresses working on each part of the apparatus are considered and a guideline for the selection of suitable materials is given on the basis of their mechanical and physical properties. Especially, the relation of the material strength to the generated pressure is explained in the case of the piston-cylinder type high-pressure clamp cell. It is also emphasized that the processing is important for the materials strength and the performance of high-pressure apparatus. In connection with recent topics of the Ni-based Russian alloy (NiCrAl alloy) and MP35N, some of their materials properties are introduced.

The pressure dependence of Tc of superconducting PrBa2Cu3Ox was studied by electrical resistance measurements under hydrostatic pressure up to 10 GPa. A large positive pressure coefficient of Tc, dTc/dP, with a maximum of 7. 3K/GPa, was observed. The coefficient was found to vary with the oxygen content of the compounds, in a similar manner as the isostructural YBa2Cu3Ox compound behaves. The present research revealed an opposite pressure effect on Tc with those reported for the Pr-substituted Y-Ba-Cu-O compounds with high Pr concentration.

A new high pressure apparatus with cubic anvil device has been developed to carry out simultaneously X-ray diffraction and electrical resistance measurement up to 10 GPa at low temperature down to 7 K. This apparatus consists mainly of a uniaxial press for pressure generation, an X-ray diffraction system with an energy dispersive detector, and a cryostat. Some experimental results of the simultaneous measurements obtained by using this apparatus are also reported.

We have studied the de Haas-van Alphen (dHvA) effect under pressure for some typical compounds of strongly correlated Ce compounds CeSb, CeB6, CeRu2Si2, CeRu2Ge2 and CeCo2. The pressure dependence of the dHvA frequencies is much larger than that expected from compressibility or that of normal metals. The pressure dependence of the effective masses have been measured in CeSb and CeB6, and it is difficult to explain that in terms of the increase of mixing with pressure.

The magnetic susceptibility and electrical resistivity in the metal-insulator (MI) transition of a mixed-valent Ti-oxide system, Y1-x CaxRTiO3, is investigated as a function of pressure. This system exhibits obviously the temperatureinduced MI transition at x=0. 3-0. 4. At the low temperature metallic phase, susceptibility, X (T), is strongly suppressed with pressure. On the other hand, in the high temperature semiconductiong phase X (T) obeying the Curie-Weiss law is not affected strongly with pressure. The coefficient of the T2-term in resistivity, A, and the residual resistivity, ρ (0), are decreases rapidly with pressure. At x=0. 375 and 0. 39, we recognize the relation of A∝X (10 K) 2 at the low temperature metallic state.

The structural and transport properties of CuIr2 (S1-xSex) 4 spinel compounds under high pressure have been studied up to 10 GPa. Resistivities of all samples were found to become insulating with increasing pressure even for the samples behaving metallic at ambient condition. When pressure was applied to the metallic samples with x=0. 9 and 1. 0, an anomalous peak appeared below 100K in the temperature dependence of the resistivity at lower pressure, but the semiconducting behaviour governed the whole temperature region at higher pressure. No structural change was observed at the temperature above and below the anomalous peak. This behaviour was discussed by the model based on some ordering of the localized charges induced by applied pressure.