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Single-crystalline samples of a new Zintl compound, Eu3Ga2P4, have been synthesized by a Ga-flux method. Eu3Ga2P4 is found to crystallize in a monoclinic unit cell, space group C2/c, isostructural to Ca3Al2As4. The structure is composed of a pair of edge-shared GaP4 tetrahedra, which link by corner-sharing to form Ga2P4 two-dimensional layers, separated by Eu2+ ions. Magnetic susceptibility showed a Curie-Weiss behavior with an effective magnetic moment consistent with the value for Eu2+ magnetic ions. Below 15 K, ferromagnetic ordering was observed and the saturation magnetic moment was 6.6 μB. Electrical resistivity measurements on a single crystal showed semiconducting behavior. Resistivity in the temperature range between 280 and 300 K was fit by an activation model with an energy gap of 0.552(2) eV. The temperature dependence of the resistivity is better described by the variable-range-hopping model for a three-dimensional conductivity, suggesting that Eu-P bonds are involved in the conductivity. A large magnetoresistance, up to −30%, is observed with a magnetic field H = 2 T at T = 100 K, suggesting strong coupling of carriers with the Eu2+ magnetic moment. [ABSTRACT FROM AUTHOR]

Unconventional superconductors have Cooper pairs with lower symmetries than in conventional superconductors. In most unconventional superconductors, the additional symmetry breaking occurs in relation to typical ingredients such as strongly correlated Fermi liquid phases, magnetic fluctuations, or strong spin-orbit coupling in noncentrosymmetric structures. In this article, we show that the time-reversal symmetry breaking in the superconductor LaNiGa2 is enabled by its previously unknown topological electronic band structure, with Dirac lines and a Dirac loop at the Fermi level. Two symmetry related Dirac points even remain degenerate under spin-orbit coupling. These unique topological features enable an unconventional superconducting gap in which time-reversal symmetry can be broken in the absence of other typical ingredients. Our findings provide a route to identify a new type of unconventional superconductors based on nonsymmorphic symmetries and will enable future discoveries of topological crystalline superconductors. Topological superconducting systems are expected to exhibit a range of exotic physics which are particularly useful for application in quantum computing technologies. Here, the authors report the synthesis of LaNiGa2 which exhibits both topological and superconducting features originating from its nonsymmorphic crystal structure. [ABSTRACT FROM AUTHOR]

We report 139La nuclear magnetic resonance data in La4Ni3O8 that reveal the presence of antiferromagnetic order below TN~105 K. This remarkable compound contains two-dimensional (2D) layers of NiO2 with unusual Ni valences. La4Ni3O8, with antiferromagnetic order of S=1/2 Ni1+ spins, is analogous to the parent compounds of the cuprate superconductors. Our data clearly reveal dramatic spectral changes and low-energy antiferromagnetic correlations associated with the onset of long-range order below TN. These critical spin fluctuations, however, do not diverge at the second-order phase transition but rather appear to be associated with a T=0 transition characteristic of 2D spin fluctuations. [ABSTRACT FROM AUTHOR]

The article discusses a study which examined the flux growth and crystal structure of two inorganic compounds with the Euln2P2 with the structure type, AIn2P2 and a structure type, BaIn2P2. It investigates the synthesis of calcium indium phosphide, strontium indium phosphide and barium indium phosphide from a reactive indium flux. Also observed are the temperature-dependent magnetoresistance and magneto-optical behavior as well as the alkaline earth analogs of the compound.

Abstract: Ln 3Co4Sn13 (Ln=La, Ce) have been synthesized by flux growth and characterized by single crystal X-ray diffraction. These compounds adopt the Yb3Rh4Sn13-type structure and crystallize in the cubic space group (No. 223) with . Lattice parameters at 298K are , , and , for the La and Ce analogues, respectively. The crystal structure consists of an Sn-centered icosahedron at the origin of the unit cell, which shares faces with eight Co trigonal prisms and 12 Ln-centered cuboctahedra. Magnetization data at 0.1T show paramagnetic behavior down to 1.8K for Ce3Co4Sn13, with per Ce3+, while conventional type II superconductivity appears below 2.85K in the La compound. Electrical resistivity and specific heat data for the La compound show a corresponding sharp superconducting transition at T c∼2.85K. The entropy and resistivity data for Ce3Co4Sn13 show the existence of the Kondo effect with a complicated semiconducting-like behavior in the resistivity data. In addition, a large enhanced specific heat coefficient at low T with a low magnetic transition temperature suggests a heavy-fermionic character for the Ce compound. Herein, the structure and physical properties of Ln 3Co4Sn13 (Ln=La, Ce) are discussed. [Copyright &y& Elsevier]

A new rare earth metal Zintl phase, Eu3In2P4, was synthesized by utilizing a metal flux method. The compound crystallizes in the orthorhombic space group Pnnm with the cell parameters a = 16.097(3) Å, b = 6.6992(13) Å, c = 4.2712(9) Å, and Z = 2 (T= 90(2) K, R1 = 0.0159, wR2 = 0.0418 for all data). It is isostructural to Sr3In2P4. The structure consists of tetrahedral dimers, [In2P2P4/2]6-, that form a one-dimensional chain along the c axis. Three europium atoms interact via a Eu-Eu distance of 3.7401(6) Å to form a straight line triplet. Single-crystal magnetic measurements show anisotropy at 30 K and a magnetic transition at 14.5 K. High-temperature data give a positive Weiss constant, which suggests ferromagnetism, while the shape of susceptibility curves (χ vs T) suggests antiferromagnetism. Heat capacity shows a magnetic transition at 14.5 K that is suppressed with field. This compound is a semiconductor according to the temperature-dependent resistivity measurements with a room-temperature resistivity of 0.005(1) Ω m and Eg = 0.452(4) eV. It shows negative magnetoresistance below the magnetic ordering temperature. The maximum magnetoresistance (Δ ρ/ ρ (H)) is 30% at 2 K with H = 5 T. [ABSTRACT FROM AUTHOR]

The reactions of the aromatic nitrogen donor ligands pyridine (py) and 4,4′-bipyridyl (4,4′-bipy) with the transition metal silylamides M{N(SiMe3)2}2 (M=Mn, Fe or Co) were investigated. Treatment of the metal amides with pyridine afforded the bispyridine complexes M{N(SiMe3)2}(py)2 (M=Mn, 1a; Fe, 2a; Co, 3a). Distillation or sublimation of 2a or 3a afforded the monopyridine complexes M{N(SiMe3)2}2(py) (M=Fe, 2b; Co, 3b). The addition of pyrazine (prz) to Mn{N(SiMe3)2}2 also yielded the bispyrazine adduct Mn{N(SiMe3)2}2(prz)2, 1b. However, the reaction of 4,4′-bipyridyl with Fe{N(SiMe3)2}2 or Co{N(SiMe3)2}2 afforded the polymeric chain-like complexes {M{N(SiMe3)2}2(4,4′-bipy)}∞ (M=Fe, 4; Co, 5). With the exception of 2b, all complexes were characterized by X-ray crystallography. The complexes 1a, 1b, 2a and 3a displayed monomeric structures and metal geometries that are based on a tetrahedron with interligand angles that deviate markedly from idealized values. Complex 3b was found to have a distorted trigonal planar geometry. In contrast, complexes 4 and 5 displayed polymeric zig-zag chain structures which have four coordinate metal centers connected by 4,4′-bipyridyl ligands. Magnetic studies indicated that complexes 1–3b have high-spin electron configurations and that the paramagnetic centers in 4 and 5 did not interact with each other through the 4,4′-bipyridyl ligands. [Copyright &y& Elsevier]

A non-magnetic piston-cylinder pressure cell is presented for solution-state NMR spectroscopy at geochemical pressures. The probe has been calibrated up to 20 kbar using in situ ruby fluorescence and allows for the measurement of pressure dependencies of a wide variety of NMR-active nuclei with as little as 10 μL of sample in a microcoil. Initial (11)B NMR spectroscopy of the H3BO3-catechol equilibria reveals a large pressure-driven exchange rate and a negative pressure-dependent activation volume, reflecting increased solvation and electrostriction upon boron-catecholate formation. The inexpensive probe design doubles the current pressure range available for solution NMR spectroscopy and is particularly important to advance the field of aqueous geochemistry., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)