Charge, lattice and magnetism across the valence crossover in EuIr2_2Si2_2 single crystals

We present a detailed study of the temperature evolution of the crystal structure, specific heat, magnetic susceptibility and resistivity of single crystals of the paradigmatic valence-fluctuating compound EuIr$_2$Si$_2$. A comparison to stable-valent isostructural compounds EuCo$_2$Si$_2$ (with Eu$^{3+}$), and EuRh$_2$Si$_2$, (with Eu$^{2+}$) reveals an anomalously large thermal expansion indicative of the lattice softening associated to valence fluctuations. A marked broad peak at temperatures around 65-75 K is observed in specific heat, susceptibility and the derivative of resistivity, as thermal energy becomes large enough to excite Eu into a divalent state, which localizes one f electron and increases scattering of conduction electrons. In addition, the intermediate valence at low temperatures manifests in a moderately renormalized electron mass, with enhanced values of the Sommerfeld coefficient in the specific heat and a Fermi-liquid-like dependence of resistivity at low temperatures. The high residual magnetic susceptibility is mainly ascribed to a Van Vleck contribution. Although the intermediate/fluctuating valence duality is to some extent represented in the interconfiguration fluctuation model commonly used to analyze data on valence-fluctuating systems, we show that this model cannot describe the different physical properties of EuIr$_2$Si$_2$ with a single set of parameters.Comment: 12 pages, 4 figures, 1 tabl

Single crystal growth and anisotropic magnetic properties of Li2Sr[Li1 − xFexN]2

Up to now, investigation of physical properties of ternary and higher nitridometalates was severely hampered by challenges concerning phase purity and crystal size. Employing a modified lithium flux technique, we are now able to prepare sufficiently large single crystals of the highly air and moisture sensitive nitridoferrate $\rm Li_2Sr[Li_{1-x}Fe_xN]_2$ for anisotropic magnetization measurements. The magnetic properties are most remarkable: large anisotropy and coercivity fields of 7 Tesla at $T = 2$ K indicate a significant orbital contribution to the magnetic moment of iron. Altogether, the novel growth method opens a route towards interesting phases in the comparatively recent research field of nitridometalates and should be applicable to various other materials.Comment: 10 pages, 5 figures, published open access in Inorganics, minor typos correcte

Structural investigations of CeIrIn5{_5} and CeCoIn5{_5} on macroscopic and atomic length scales

For any thorough investigation of complex physical properties, as encountered in strongly correlated electron systems, not only single crystals of highest quality but also a detailed knowledge of the structural properties of the material are pivotal prerequisites. Here, we combine physical and chemical investigations on the prototypical heavy fermion superconductors CeIrIn${_5}$ and CeCoIn${_5}$ on atomic and macroscopic length scale to gain insight into their precise structural properties. Our approach spans from enhanced resolution X-ray diffraction experiments to atomic resolution by means of Scanning Tunneling Microscopy (STM) and reveal a certain type of local features (coexistence of minority and majority structural patterns) in the tetragonal HoCoGa$_5$-type structure of both compounds.Comment: 8 pages, 5 figures, submitted to JPSJ (SCES 2013

Refinement of the crystal structure of palladium gallium (1:1), PdGa

PdGa, cubic, P2(1)3 (no. 198), a = 4.89695(6) angstrom, V = 117.

Crystal structure of cobalt manganese monoaqua catena-[monohydrogenborate-tris(hydrogenphosphate)], (Co0.6Mn0.4)(2)(H2O) [BP3O9(OH)(4)]

BCo1.20H6Mn0.80O14P3, orthorhombic, P2(1)2(1)2(1) (no. 19), a = 7.1355(6) angstrom, b = 8.7321(8) angstrom, c = 16.405(2) angstrom, V = 1022.2 angstrom(3), Z = 4, R-gt(F) = 0.049, wR(ref)(F-2) = 0. 119, T = 295 K

Tricyanidoferrates(−IV) and ruthenates(−IV) with non‐innocent cyanido ligands

Exceptionally electron-rich, nearly trigonal-planar tricyanidometalate anions [Fe(CN)(3)](7-) and [Ru(CN)(3)](7-) were stabilized in LiSr3[Fe(CN)(3)] and AE(3.5)[M(CN)(3)] (AE=Sr, Ba; M=Fe, Ru). They are the first examples of group 8 elements with the oxidation state of -IV. Microcrystalline powders were obtained by a solid-state route, single crystals from alkali metal flux. While LiSr3[Fe(CN)(3)] crystallizes in P6(3)/m, the polar space group P6(3) with three-fold cell volume for AE(3.5)[M(CN)(3)] is confirmed by second harmonic generation. X-ray diffraction, IR and Raman spectroscopy reveal longer C-N distances (124-128 pm) and much lower stretching frequencies (1484-1634 cm(-1)) than in classical cyanidometalates. Weak C-N bonds in combination with strong M-C pi-bonding is a scheme also known for carbonylmetalates. Instead of the formal notation [Fe-IV(CN-)(3)](7-), quantum chemical calculations reveal non-innocent intermediate-valent CN1.67- ligands and a closed-shell d(10) configuration for Fe, that is, Fe2-

Nanoporous titanium borophosphates with rigid gainesite-type framework structure

China Scholarship Council (CSC); National Natural Science Foundation of China [40972035]Nanoporous titanium borophosphates have been synthesized which exhibit a rigid gainesite-type framework of polyhedra. The open-framework character is supported by the reversibility of de-and rehydration processes

Ultrasmall functional ZnO2 nanoparticles: synthesis, characterization and oxygen release properties

Ultrasmall zinc peroxide nanoparticles with diameter between 3.3 +/- 0.9 and 14.4 +/- 5.2 nm were synthesized by a simple and fast hydrothermal synthesis method. The precursor zinc acetate dihydrate was oxidized with hydrogen peroxide in aqueous media using a high-pressure impinging-jet reactor (MRT CR5, Microfluidics (R)). The combination of the high process pressure of 1400 bar and the special reaction chamber geometry minimized nanoparticle aggregation and limited the crystal growth, which resulted in very small and uniform particles. The zinc peroxide nanoparticles were in situ stabilized by bis[2-(methacryloyloxy)ethyl]phosphate providing excellent colloidal stability in water and integration of functional groups (polymerizable vinyl groups and adhesion-promoting phosphate groups). The obtained nanoparticles were characterized by XRD, TGA, TGA-MS, TEM, HR-TEM, Raman spectroscopy and zeta potential measurements. Furthermore the oxygen release from ZnO2 nanoparticles was analyzed. The oxygen release can be triggered by two different mechanisms: thermal decomposition in the dry state (T < 190 degrees C) and hydrolysis in water at pH < 8

Anomalous Thermal Expansion of HoCo0.5Cr0.5O3 Probed by X-ray Synchrotron Powder Diffraction

Abstract Mixed holmium cobaltite-chromite HoCo0.5Cr0.5O3 with orthorhombic perovskite structure (structure type GdFeO3, space group Pbnm) was obtained by solid state reaction of corresponding oxides in air at 1373 K. Room- and high-temperature structural parameters were derived from high-resolution X-ray synchrotron powder diffraction data collected in situ in the temperature range of 300–1140 K. Analysis of the results obtained revealed anomalous thermal expansion of HoCo0.5Cr0.5O3, which is reflected in a sigmoidal temperature dependence of the unit cell parameters and in abnormal increase of the thermal expansion coefficients with a broad maxima near 900 K. Pronounced anomalies are also observed for interatomic distances and angles within Co/CrO6 octahedra, tilt angles of octahedra and atomic displacement parameters. The observed anomalies are associated with the changes of spin state of Co3+ ions and insulator-metal transition occurring in HoCo0.5Cr0.5O3