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We have studied the superconducting properties of CeTIn5 (T=Rh, Ir) under high pressures by means of electrical resistivity measurements and determined the pressure–temperature phase diagrams for the superconducting transition. For both systems, the superconductivity exists in a wide pressure range, 1.5⩽P⩽6.5 GPa for CeRhIn5 and 0⩽P⩽5.2 GPa for CeIrIn5. [Copyright &y& Elsevier]

We measured the pressure dependence of in-plane resistivity pab in the recently discovered iron-based superconductor Ca10(Ir4As8)(Fe2-x IrxAs2)5, which shows a unique structural phase transition in the absence of magnetic ordering, with a superconducting transition temperature Tc = 16 K and a structural phase transition temperature Ts ≃ 100 K at ambient pressure. Tc and Ts are suppressed on applying pressure and disappear at approximately 0.5 GPa, suggesting a relationship between superconductivity and structure. Ca10(Ir4As8)(Fe2-x IrxAs2)5 is a rather rare example in which the superconductivity appears only in a lowtemperature ordered phase. The fact that the change in the crystal structure is directly linked with superconductivity suggests that the crystal structure as well as magnetism are important factors governing superconductivity in iron pnictides. [ABSTRACT FROM AUTHOR]

Superconducting phases of (NH3)yMxFeSe1-zTez have been synthesized by the intercalation of metal atoms (M: Li, Na, Ca) into FeSe and FeSe0.5Te0.5 using a low-temperature liquid NH3 technique. The superconducting transition temperature (Tc) is 31.5 K for Na-doped FeSe, and for Li-, Na-, and Ca-doped FeSe0.5Te0.5 it is 26, 22, and 17 K, respectively. The 31.5 K superconducting is the superconducting phase in ammoniated Na-doped FeSe. The Tc is lower than that (onset Tc = 46 K) of the superconducting phase reported previously. The reason why the Tc of this phase is lower is discussed based on the structure. The pressure dependences of Tc in the (NH3)yNa0.5FeSe and (NH3)yNa0.4FeSe0.5Te0.5 samples have been measured and a negative pressure dependence is observed; i.e., a decrease in lattice constant c leads to a decrease in Tc, consistent with the behavior of (NH3)yCs0.4FeSe reported previously by our group. Furthermore, the magnetic behavior of (NH3)yNa0.4FeSe0.5Te0.5 has been fully investigated at different applied magnetic fields (H) to determine the critical magnetic field. This is a successful metal intercalation into FeSe1-zTez (z≠0) and an observation of superconductivity. [ABSTRACT FROM AUTHOR]

Abstract: An overview of the crystal structures and physical properties of the recently discovered iron–platinum–arsenide superconductors, Ca10(Pt n As8)(Fe2−x Pt x As2)5 ( and 4), which have a superconducting transition temperature up to 38 K, is provided. The crystal structure consists of superconducting Fe2As2 layers alternating with platinum–arsenic layers, Pt n As8. The upper critical field , hydrostatic pressure dependence of superconducting transition temperature , and normal-state magnetic susceptibility are reported. [Copyright &y& Elsevier]

Antiferromagnet Mn3P with Neel temperature TN = 30 K is composed of Mn tetrahedrons and zigzag chains formed by three inequivalent Mn sites. Due to the nearly frustrated lattice with many short Mn-Mn bonds, competition of the exchange interactions is expected. We here investigate the magnetic structure and physical properties including pressure effect in single crystals of this material, and reveal a complex yet well-ordered helimagnetic structure. The itinerant character of this materials is strong, and the ordered state with small magnetic moments is easily suppressed under pressure, exhibiting a quantum critical point at ~ 1.6 GPa. The remarkable mass renormalization, even in the ordered state, and an incoherent-coherent crossover in the low-temperature region, characterize an unusual electronic state in Mn3P, which is most likely effected by the underlying frustration effect. [ABSTRACT FROM AUTHOR]

The 5d-transition-metal pyrochlore oxide Cd2Re2O7, which was recently suggested to be a prototype of the spin-orbit-coupled metal [Phys. Rev. Lett. 115, 026401 (2015)], exhibits an inversion-symmetry-breaking (ISB) transition at 200 K and a subsequent superconductivity below 1 K at ambient pressure. We study the crystal structure at high pressures up to 5 GPa by means of synchrotron x-ray powder diffraction. A rich structural phase diagram is obtained, which contains at least seven phases, and is almost consistent with the electronic phase diagram determined by previous resistivity measurements. Interestingly, the ISB transition vanishes at ∼4GPa where the enhancement of the upper critical field was observed in resistivity. Moreover, it is shown that the point groups at 8 K, probably kept in the superconducting phases, sequentially transform into piezoelectric, ferroelectric, and centrosymmetric structures on the application of pressure. [ABSTRACT FROM AUTHOR]

The structural and superconducting properties of the Bi-based superconductor Bi 2 Rh 3 (Se 1- x S x ) 2 were investigated over a wide pressure range. Bi 2 Rh 3 Se 2 is a superconductor with a superconducting transition temperature, T c , of less than ∼1.0 K, whereas Bi 2 Rh 3 S 2 is a nonsuperconductor. The former shows a clear charge density wave (CDW) phase transition at 240 K and the latter shows a first-order structural phase transition at 165 K, providing the supercell structure. Both compounds have the same crystal structure at ambient temperature and pressure (monoclinic, space group of C 2/ m (No. 12)). This implies the possible formation of solid solution-like phases Bi 2 Rh 3 (Se 1- x S x ) 2 . In this study, we prepared Bi 2 Rh 3 (Se 1- x S x ) 2 ( x = 0-1.0) and investigated its superconducting properties and phase transitions at different x values. Because the superconducting properties and temperature causing the phase transition ( T pt ) are quite different between Bi 2 Rh 3 Se 2 and Bi 2 Rh 3 S 2 , their variation against x is quite intriguing from the viewpoint of the pursuit of physical properties via the replacement of Se with S. In this study, the features of the superconductivity and crystal structure against x were fully explored to depict the phase diagram. Moreover, we investigated the pressure ( p ) dependence of superconductivity and phase transition (CDW or the first-order structural transition) to clarify the interplay between the two ordered states.

We report the direct observation of dioxygen molecules physisorbed in the nanochannels of a microporous copper coordination polymer by the MEM (maximum entropy method)/Rietveld method, using in situ high-resolution synchrotron x-ray powder diffraction measurements. The obtained MEM electron density revealed that van der Waals dimers of physisorbed O2 locate in the middle of nanochannels and form a one-dimensional ladder structure aligned to the host channel structure. The observed O-O stretching Raman band and magnetic susceptibilities are characteristic of the confined O2 molecules in one-dimensional nanochannels of CPL-1 (coordination polymer 1 with pillared layer structure).