Nematic superconducting state in iron pnictide superconductors.

Nematic order often breaks the tetragonal symmetry of iron-based superconductors. It arises from regular structural transition or electronic instability in the normal phase. Here, we report the observation of a nematic superconducting state, by measuring the angular dependence of the in-plane and out-of-plane magnetoresistivity of BaKFeAs single crystals.

Correction: New layered cobalt oxyfluoride, SrCoOF.

Correction for 'New layered cobalt oxyfluoride, SrCoOF' by Yoshihiro Tsujimoto et al., Chem. Commun.

Local destruction of superconductivity by non-magnetic impurities in mesoscopic iron-based superconductors.

The determination of the pairing symmetry is one of the most crucial issues for the iron-based superconductors, for which various scenarios are discussed controversially. Non-magnetic impurity substitution is one of the most promising approaches to address the issue, because the pair-breaking mechanism from the non-magnetic impurities should be different for various models. Previous substitution experiments demonstrated that the non-magnetic zinc can suppress the superconductivity of various iron-based superconductors.

Exploration of new superconductors and functional materials, and fabrication of superconducting tapes and wires of iron pnictides.

This review shows the highlights of a 4-year-long research project supported by the Japanese Government to explore new superconducting materials and relevant functional materials. The project found several tens of new superconductors by examining ∼1000 materials, each of which was chosen by Japanese experts with a background in solid state chemistry. This review summarizes the major achievements of the project in newly found superconducting materials, and the fabrication wires and tapes of iron-based superconductors; it incorporates a list of ∼700 unsuccessful materials examined for superconductivity in the project.

High-pressure synthesis, crystal structures, and properties of ScRhO3 and InRhO3 perovskites.

ScRhO3 and InRhO3 perovskites were synthesized at a high pressure of 6 GPa and a high temperature of 1500 K. Crystal structures of ScRhO3 and InRhO3 were studied with synchrotron X-ray powder diffraction at 293 and 134 K. ScRhO3 and InRhO3 have a rarely observed monoclinic superstructure of the GdFeO3-type structure (space group P21/n, a = 7.

Crystal structural, magnetic, and transport properties of layered cobalt oxyfluorides, Sr2CoO(3+x)F(1-x) (0 ≤ x ≤ 0.15).

The crystal structure of the layered cobalt oxyfluoride Sr(2)CoO(3)F synthesized under high-pressure and high-temperature conditions has been determined from neutron powder diffraction and synchrotron powder diffraction data collected at temperatures ranging from 320 to 3 K. This material adopts the tetragonal space group I4/mmm over the measured temperature range and the crystal structure is analogous to n = 1 Ruddlesden-Popper type layered perovskite. In contrast to related oxyhalide compounds, the present material exhibits the unique coordination environment around the Co metal center: coexistence of square pyramidal coordination around Co and anion disorder between O and F at the apical sites.

Growth of single-crystal Ca10(Pt4As8)(Fe(1.8)Pt(0.2)As2)5 nanowhiskers with superconductivity up to 33 K.

Single-crystal Ca(10)(Pt(4)As(8))(Fe(1.8)Pt(0.2)As(2))(5) superconducting (SC) nanowhiskers with widths down to hundreds of nanometers were successfully grown in a Ta capsule in an evacuated quartz tube by a flux method.

Low-temperature vacuum reduction of BiMnO3.

Low-temperature vacuum reduction was used for the preparation of the oxygen-deficient BiMnO(2.81) sample in a bulk form from stoichiometric BiMnO(3). The transformation occurs in vacuum better than 10(-3) Pa at a narrow temperature range of 570-600 K.

Perovskite, LiNbO3, corundum, and hexagonal polymorphs of (In(1-x)M(x))MO3.

LiNbO(3) (LN), corundum (cor), and hexagonal (hex) phases of (In(1-x)M(x))MO(3) (x = 0.143; M = Fe(0.5)Mn(0.

Structural evolution and properties of solid solutions of hexagonal InMnO3 and InGaO3.

Solid solutions InMn(1-x)Ga(x)O(3) (0 ≤ x ≤ 1) have been investigated using magnetic, dielectric, specific heat, differential scanning calorimetry (DSC), and high-temperature powder synchrotron X-ray diffraction (HT-SXRD) measurements. It was found that samples with 0.5 ≤ x ≤ 1 crystallize in space group P6(3)/mmc with a ~ 3.

Coexistence of light and heavy carriers associated with superconductivity and antiferromagnetism in CeNi0.8Bi2 with a Bi square net.

We found that the ZrCuSiAs-type crystal CeNi(0.8)Bi(2) with a layered structure composed of alternate stacking of [CeNi(x)Bi(1)](δ+) and Bi(2)(δ-) exhibits a superconductive transition at ∼4  K. The conductivities, magnetic susceptibilities, and heat capacities measurements indicate the presence of two types of carriers with notable different masses, i.

New layered cobalt oxyfluoride, Sr2CoO3F.

The first Ruddlesden-Popper type layered cobalt oxyfluoride, Sr(2)CoO(3)F, has been synthesized under a pressure of 6 GPa at 1700 °C and shown to adopt a K(2)NiF(4)-type structure with distorted square pyramidal coordination around Co and with O/F disorder at the apical sites.

Structural studies of a mixed-valence state in the incommensurate composite crystal SrCoO.

The incommensurate modulated crystal structure of the hexagonal cobalt oxide SrCoO has been studied using a four-dimensional (4D) superspace profile analysis of neutron powder diffraction data. SrCoO is a composite crystal that consists of the [CoO] and [2Sr] subsystems. The [CoO] subsystem forms 1D chains that run parallel to the -axis and consist of face-sharing CoO polyhedra with octahedral () and trigonal prismatic () coordinations.

Effects of oxygen content on Bi3Mn3O(11+delta): from 45 K antiferromagnetism to room-temperature true ferromagnetism.

The effects of oxygen content on the structural, physical, and chemical properties of Bi(3)Mn(3)O(11) with KSbO(3)-type structure have been investigated. It was found that the oxygen content in Bi(3)Mn(3)O(11+delta) can vary over a wide delta range, keeping the same cubic structure (space group Pn3, a = 9.12172(5) A for delta = -0.

Pressure-induced spin-state transition in BiCoO3.

The structural and electronic properties of BiCoO(3) under high pressure have been investigated. Synchrotron X-ray and neutron powder diffraction studies show that the structure changes from a polar PbTiO(3) type to a centrosymmetric GdFeO(3) type above 3 GPa with a large volume decrease of 13% at room temperature revealing a spin-state change. The first-order transition is accompanied by a drop of electrical resistivity.

Crystal growth and structure and magnetic properties of the 5d oxide Ca3LiOsO6: extended superexchange magnetic interaction in oxide.

Crystals of the newly synthesized compound Ca(3)LiOsO(6) were grown by a flux method using LiCl and KCl, followed by single-crystal X-ray diffraction (XRD), low-temperature powder XRD, and measurements of ac and dc magnetic susceptibility and specific heat. The data indicate that Ca(3)LiOsO(6) has a fully opened electronic gap with an antiferromagnetic ordered state, consistent with suggestions from the first-principles study. The observed magnetic transition temperature is 117 K, too high to be caused only by a direct spin-spin interaction.

Crystal and magnetic structures and properties of BiMnO(3+delta).

Crystal and magnetic structures of BiMnO(3+delta) (delta = 0.03, 0.08, and 0.

Bi3Mn3O11: a new KSbO3-type random ferrimagnet with high T(C).

A new compound, Bi(3)Mn(3)O(11), with a KSbO(3)-type structure was prepared using a high-pressure technique. Its structural, chemical, and magnetic properties have been investigated. Bi(3)Mn(3)O(11) was shown to be a ferrimagnet with rather high T(C) despite the random distribution of manganese ions with different oxidation states in one site.

Synthesis and magnetic and charge-transport properties of the correlated 4d post-perovskite CaRhO3.

A high-quality polycrystalline sample of the correlated 4d post-perovskite CaRhO(3) (Rh(4+): 4d(5), S(el) = 1/2) was attained under a moderate pressure of 6 GPa. Since the post-perovskite is quenchable at ambient pressure/temperature, it can be a valuable analogue of the post-perovskite MgSiO(3) (stable higher than 120 GPa and unstable at ambient pressure), which is a significant key material in earth science. The sample was subjected for measurements of charge-transport and magnetic properties.

Peculiar high-pressure behavior of BiMnO3.

High-pressure structural properties of perovskite-type BiMnO(3) have been investigated by synchrotron X-ray powder diffraction at room temperature. A new monoclinic phase having P2(1)/c symmetry was found between about 1.5 and 5.

Structure of the monoclinic-form misfit-layer compound, (Ca0.85OH)2alpha CoO2 (alpha approximately 0.57822).

The incommensurate modulated crystal structure of the new misfit-layer calcium cobalt oxide (Ca0.85OH)2alphaCoO2 was investigated using a superspace-group formalism with synchrotron X-ray diffraction data. The compound is a kind of composite crystal that consists of two interpenetrating subsystems, [CoO2]infinity layers containing triangular lattices formed by edge-sharing CoO6 octahedra, separated from each other by [2Ca0.