We report the pressure dependences of the superconducting transition temperature (Tc) in several perovskite-type Fe-based superconductors through the resistivity measurements up to ∼ 4 GPa. In Ca4(Mg,Ti)3Fe2As2Oy with the highest Tc of 47 K in the present study, the Tc keeps almost constant up to ∼ 1 GPa, and starts to decrease above it. From the comparison among several systems, we obtained a tendency that low Tc with the longer a-axis length at ambient pressure increases under pressure, but high Tc with the shorter a-axis length at ambient pressure hardly increases. We also report the 75 As-NMR results on Sr2VFeAsO3. NMR spectrum suggests that the magnetic ordering occurs at low temperatures accompanied by some inhomogeneity. In the superconducting state, we confirmed the anomaly by the occurrence of superconductivity in the nuclear spin lattice relaxation rate 1/T1, but the spin fluctuations unrelated with the superconductivity are dominant. It is conjectured that the localized V-3d moments are magnetically ordered and their electrons do not contribute largely to the Fermi surface and the superconductivity in Sr2VFeAsO3.

We report a study of the charge-density-wave (CDW) behavior in LaAgSb(2) by means of electrical resistivity, Seebeck coefficient, thermal conductivity, specific heat, and nuclear magnetic resonance (NMR) measurements. Except for the Seebeck coefficient, apparent indications of CDW ordering at around 207 K were noticed in the physical quantities investigated. On the other hand, all measured physical properties are insensitive to the second CDW formation (∼184 K), as the transition character is considerably weaker than the high-temperature one. Further, analyses of the thermal conductivity and NMR Knight shift data revealed that the observed variations are essentially of electronic origin. The present findings are in good agreement with the previous results, indicating that the high-temperature CDW ordering is associated with a small gapping of the Fermi surface with a minor periodic displacement of the crystal lattice in LaAgSb(2).