We described an integrated-fin gasket technique for the palm cubic-anvil apparatus specialized for the high-pressure and low-temperature measurements. By using such a gasket made from the semi-sintered MgO ceramics and the tungsten-carbide anvils of 2.5 mm square top, we successfully generate pressures over 16 GPa at both room and cryogenic temperatures down to 0.5 K. We observed a pressure self-increment for this specific configuration and further characterized the thermally induced pressure variation by monitoring the antiferromagnetic transition temperature of chromium up to 12 GPa. In addition to enlarge the pressure capacity, such a modified gasket also improves greatly the surviving rate of electrical leads hanging the sample inside a Teflon capsule filled with the liquid pressure-transmitting medium. These improvements should be attributed to the reduced extrusion of gasket materials during the initial compression.

We report the effect of hydrostatic pressure on the electronic state of the antiferromagnet UIrGe, which is isostructural and isoelectronic with the ferromagnetic superconductors UCoGe and URhGe. A series of electrical resistivity measurements in a piston-cylinder-type cell and a cubic-anvil cell were performed at hydrostatic pressures up to 15 GPa. The Néel temperature decreases with increasing pressure. We constructed a p-T phase diagram and estimated the critical pressure pc, where the antiferromagnetism vanishes, as  12 GPa. The antiferromagnetic/paramagnetic transition appears to be first order. We suggest a scenario of competing antiferromagnetic inter-J-and ferromagnetic intra-J*-chain interactions in UIrGe. A moderate increase in the effective electron mass was detected in the vicinity of pc. A discussion of the electronic specific heat  and electron-electron correlation term A using the KadowakiWoods relation is given.

The two-stage 6-8 multi-anvil (MA8) apparatus is an important large-volume, high-pressure technique that has been widely used in the high pressure mineralogy and material synthesis, mainly at room temperature or above. Recently, we have successfully developed a two-stage MA8 apparatus for low-temperature physical property measurements. The first-stage anvils at top and bottom sides are fabricated as a single piece in order to reduce the total size of the cylindrical module, which is put in a top-loading high pressure cryostat and compressed by a 1000 ton hydraulic press. A castable, split octahedral gasket with integrated fin was specifically designed in order to introduce the electrical leads from the inside sample container filled with a liquid pressure transmitting medium. By using tungsten carbide (WC) second-stage cubes with a truncated edge length of 3 mm and an octahedral gasket with an edge length of 6 mm, we have successfully generated pressure over 20 GPa at room temperature. Since the high pressure limit can be pushed to nearly 100 GPa by using the sintered diamond second-stage cubes, our MA8 apparatus has a great potential to expand the current pressure capacity for precise low-temperature measurements with a large sample volume. Edited by: A. Goñi, A. Cantarero, J. S. Reparaz

We have studied the effect of hydrostatic pressure on the superconducting and normal state properties of non-centro symmetric (NCS) superconductor Re5.5Ta using magneto transport, magnetization and band structure studies. The superconducting transition temperature (T_c) reveals a modest decrease of ~ 0.52 K as the external pressure raised to 8 GPa. We found that the Maki parameter, αM>1, both at ambient and high pressure suggests the significant role of Pauli pair breaking effect. Furthermore, the lower critical field was found to be decreased with the rate of -1.74 mT/GPa as pressure increases to 1.05 GPa. The analysis of thermally activated flux flow region of ρ(T,H) by Arrhenius equation reveals the coexistence of single and collective vortex states. Further analysis of critical current density indicates that the surface and volume pinning center coexist and remain unaffected with varying pressure. The band structure calculations were done using density functional theory reveals a large bulk modulus, B0~ 289 GPa with B0 ' ~ 3.7 suggesting poor compressibility. In addition, we found that the density of states at the Fermi level reduces barely even up to 20 GPa, consistent with the experimental observation of robust superconductivity under compression.

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A "palm" cubic-anvil pressure cell (PCAC) having an outer diameter of 60 mm, the smallest cubic-anvil cell to date, was fabricated to insert in a large-bore superconducting magnet. The pressure cell has a sample space of ϕ 2.5 × 1.5 mm 2 , which is fairly large for a pressure cell that can reach a high pressure above 4 GPa. Pressure homogeneity was monitored from the 63 Cu nuclear-quadrupole-resonance linewidth of Cu 2 O up to 6.7 GPa. The linewidth first increased with increasing pressure up to 4 GPa and then saturated above 4 GPa. The pressure homogeneity was better than that of a piston-cylinder pressure cell. The PCAC is advantageous because a large sample space and high pressure homogeneity are secured even at high pressures.

Resistivity, magnetoresistance, and upper critical field, have been comprehensively studied for the bismuth (Bi)-III superconducting phase in the pressure range of 2.9 GPa ⩽ P⩽ 6.2 GPa. It is discovered that the transition temperature T c of the Bi-III phase is gradually suppressed with increasing pressure. Strikingly, the temperature-dependent resistivity above T c in the Bi-III region reveals notable non-Fermi-liquid behaviors, resembling many unconventional superconducting systems. As the pressure increases, the magnetoresistance effect progressively grows and reaches a maximum value of 212% at pressure ∼6.2 GPa and field of 5 T, indicating a possible contribution to the charge conduction by Dirac electrons. Moreover, the zero-temperature upper critical field for the Bi-III phase displays relatively low values concerning the moderate T c values, and the reduced upper critical field for different pressures deviates from the single-band Werthamer–Helfand–Hohenberg model. These unusual normal state transport properties and unique behavior of the upper critical field point to possible unconventional superconductivity for the Bi-III superconducting phase.