[en] The crystal structures of the R₂Pd₂Pb (R=Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, and Lu) compounds were determined using X-ray powder diffraction. The investigated compounds crystallize with Mo₂FeB₂ structure type (space group P4/mbm, Pearson code tP10). The importance of stabilization by polar intermetallic R-Pd bonding is underscored by a bonding analysis derived from electronic band structure calculations

[en] Multifilamentary wires of NbTi have been irradiated at 4.2 K with 30-GeV protons and the changes in critical current I/sub c/ measured in situ in fields up to 4 T. Reductions of I/sub c/ of 20% were found for a fluence of 1.5 x 10¹⁸ p/cm². Annealing to room temperature recovers 60--70% of the I/sub c/ degradation. The decrease in I/sub c/ is attributed to an increase in the Ginzburg-Landau parameter kappa of cell cores relative to the dislocation cell walls, thereby lowering the pinning strength of the cell walls. This increase in kappa is directly related to an increasing radiation-induced normal-state resistivity. A saturation of the decreases in I/sub c/ is indicated for low-temperature proton irradiation in keeping with an observed saturation following high-fluence ambient-temperature neutron irradiation. Evidence is presented indicating that multiple annealing over the fluence life of a NbTi magnet operating in a radiation field will minimize the accumulated reduction in I/sub c/

[en] Nb_0.89Fe_0.93Te₂ and Ta_0.77Fe_0.90Te₂ were prepared by chemical transport reactions. The crystal structures of both compounds were determined using X-ray single crystal methods. The structures of the layer compounds Nb_0.89Fe_0.93Te₂ (Pmna, Z = 2, a = 7.951(1) A, b = 7.241(1) A, c = 6.233(1) A) and Ta_0.77Fe_0.90Te₂ (Pmna, Z = 2, a = 7.890(2) A, b = 7.252(2) A, c = 6.192(1) A) are based on a hexagonal close packing of Te atoms. Approximately one-half of the octahedral holes in this packing are occupied by Nb (Ta) atoms, about one-quarter of the tetrahedral holes are occupied by Fe atoms. The relationship to the NiAs structure type is discussed. (orig.)

No abstract available

[en] An improved technique for the preparation of solid specimens suitable for X-ray absorption measurements is described which is especially useful for air or water sensitive materials. The finely powdered materials are enclosed in a polymer matrix. Homogeneous, stable, and uniformly thick films can be obtained by this method. The capabilities of the technique have been tested within a series of iron and cobalt compounds. (orig.)

[en] [TaTe₄]₄[PtI₆]I₂ was synthesized from the elements at 680 C. Its crystal structure was determined using single crystal methods. The structure of the quasi one-dimensional compound [TaTe₄]₄[PtI₆]I₂ (P anti 1, Z=1, a=16.831(1), b=17.740(1), c=19.018(1) A, α=93.57 , β=16.831(1), b=17.740(1), c=19.018(1) A, α=93.57 , β=94.08 , γ=102.09 ) consists of Ta(Te₂)₂ chains separated by PtI₆ groups and I atoms. The formal oxidation state assignment [(Ta⁵⁺)(Te₂^2-)₂]₄[(Pt⁴⁺)(I^-)₆](I^-)₂ indicates that semiconducting properties are to be expected for this material. (orig.)

[en] We synthesized a series of double perovskites A₂FeReO₆ (A=Ca, Sr, Ba) with Curie temperatures above room-temperature. Neutron and X-ray diffraction analysis have been performed in order to determine the structural and (local) magnetic properties of these materials. While Ba₂FeReO₆ stays cubic over the whole temperature range we examined, the Sr-compound shows a tetragonal distortion of the perovskite structure which does not completely vanish up to about 520 K far above T_C. Ca₂FeReO₆ has a monoclinic unit cell at high temperatures. Below 400 K a phase separation in two monoclinic phases with identical cell volume is observed in neutron scattering

[en] The search for magnetic analogues of superconducting compounds has lead to the discovery of compounds with giant magnetoresistance. For example, a colossal negative magnetoresistance of up to 20% at 180 K has been measured for the chalcospinel Fe_0.5Cu_0.5Cr₂S₄. Here spin-polarized ab-initio band structure calculations are performed on the title compound in order to gain an understanding of its electronic and magnetic behavior, the structural information for these calculations being obtained from neutron diffraction data. The valency of iron is also investigated by temperature-dependent Moessbauer spectroscopy. (orig.)

[en] Electrochemical copper intercalation in ZrTe₃ yields the new metallic ternary phase Cu_xZrTe₃ with a maximum stoichiometry of x=1.9. The charge is balanced by filling the σ* antibonding Te p bands, as monitored by XANES spectroscopy. The reaction is accompanied by an increase in the a lattice dimension of 9%. This observation is explained by theoretical calculations. (orig.)

No abstract available