[en] We prepared various RuSr₂Nd_xGd_1-xCu₂O₈ samples with systematically varying Nd amounts by x=0, 0.09, 0.18 and 0.35. The solid state route involved mixed oxides (Nd_xGd_1-x)₂O₃ obtained by coprecipitation. The XRD and microstructural analysis showed that a high phase purity was obtained. The Nd solubility limit can be placed between x=0.18 and x=0.35. The superconducting transition temperature dramatically decreased with increasing Nd content, confirming that Nd entered the lattice. The field dependence of superconducting transitions exhibited a polycrystalline behaviour

[en] We present structural and physical data obtained on Ru (Gd)-1212 compounds submitted, after solid state preparation, to different annealing procedures and thermal treatment. The samples were characterized by XRPD and TEM analysis. In addition structural refinement was performed according to the Rietveld method. Variations of both the superconducting and magnetic properties are presented and discussed

[en] RuSr₂Nd_xGd_1-xCu₂O₈ samples (x=0, 0.03, 0.06 and 0.12) were synthesised by a solid state route, using mixed rare earth oxides (Nd_xGd_1-x)₂O₃, prepared by a co-precipitation method, as precursors. Magnetoresistance measurements showed that the resistive transition temperature decreased and broadened with increasing Nd doping, suggesting that Nd really entered the lattice. The resistive transition curves in applied field exhibited typical polycrystalline behaviour with two peaks in their first derivative, identified as intra and intergrain superconducting transitions. XRD data also supported the fact that Nd ion entered the Ru-1212 lattice, yielding an ordered tetragonal structure at low Nd doping level. At higher Nd concentrations, the structure becomes disordered probably due to Nd/Sr solid solution

[en] The complex Young's modulus, E, of RuSr₂GdCu₂O₈ was measured for the first time in the temperature range from 1.5 up to 900 K. In the paramagnetic phase the real part of the Young's modulus decreases almost linearly with T, in agreement with the usual quasiharmonic approximation of the lattice dynamics described by the Debye model. A Debye temperature of about 390 K well reproduces the experimental data, in agreement with θ_D obtained by means of specific heat measurements performed by other authors. However, around the ferromagnetic transition the real part of E is affected by the onset of the magnetic order, slightly decreasing from the expected Debye behavior down to about 90 K, evidencing a magnetoelastic coupling in RuSr₂GdCu₂O₈. On further cooling, E' increases, becoming greater than the value expected from the Debye model

[en] In this work we report on the variations observed in the properties of sintered RuSr₂GdCu₂O₈ (Ru-1212) subjected to annealing and deoxygenation routes. These treatments change in an important way both the structural features as observed by X-ray diffraction data, Rietveld refinement and TEM, and the physical properties as observed by transport and magnetic measurements. All these data are presented and discussed

[en] Filled skutterudites are among the most promising thermoelectric materials, and the obtainment of monophasic samples is crucial for the study of their transport properties. In this work, a differential thermal analysis study was performed on samples belonging to the Sm_y(Fe_xNi_1-x)₄Sb₁₂ system with the aim to determine the most proper annealing temperature to possibly obtain skutterudite monophasic samples, and to study the effect of Sm addition on the thermodynamics of the Fe-Ni-Sb system. Samples were prepared through the traditional procedure consisting in melting–quenching–annealing the starting elements. DTA analyses were carried out on annealed samples, and results were interpreted using the Fe₂₅Sb₇₅-Ni₂₅Sb₇₅ pseudobinary phase diagram taken from the literature as a starting point. They reveal that 870 K is the best annealing temperature, being the formation of a liquid phase just above this point; moreover, the Sm introduction results in widening the one-phase skutterudite stability region toward both higher temperatures and higher Fe concentrations compared with the Sm-free system.

[en] A stability study of perovskitic LaREO₃ oxides (RE = Dy, Ho, Er, Tm, Yb, Lu) as a function of temperature was undertaken. A correlation between the Goldschmidt t value and the perovskitic stability field amplitude was found: the latter widens as t increases. Magnetic measurements, performed on all the perovskitic samples, showed that t is also related to the exchange interactions. LaREO₃ oxides were synthesized by thermal decomposition of the corresponding coprecipitated oxalates at temperatures ranging between 600 and 1800 ^oC. Simultaneous differential thermal and thermogravimetric analyses showed that all the La-RE mixed oxalates decompose similarly. All the oxides, except LaDyO₃, crystallize in the perovskitic form in a temperature range that depends on the ionic size difference between La and the smaller rare earth; above and below the perovskitic stability field, the B or C form, typical of rare earth sesquioxides, is present. Rietveld refinements, carried out on all the LaREO₃ samples synthesized at 1200 ^oC, showed the occurrence of an orthorhombic distorted perovskitic structure belonging to the Pnma space group.

[en] Orthorhombic LaErO₃ and cubic (La_0.5 Ln _0.5)₂O₃ oxides (Ln: Er, Dy) were examined by neutron powder diffraction between 1.5 K and 15 K in order to investigate their crystallographic and magnetic structures. At 1.5 K both LaErO₃ and (La_0.5Er_0.5)₂O₃ display a magnetic moments ordering, whereas for (La_0.5Dy_0.5)₂O₃ only short range magnetic correlations can be argued, suggesting a possible magnetic moments ordering at lower temperature. LaErO₃ is characterized by a magnetic wavevector k  =  (0, 0, 0) and forms an antiferromagnetic G _x C _y A _z-type structure belonging to the $Pnma$ Shubnikov group with a total magnetic moment of 6.78(3) μ _B. The antiferromagnetic structure of (La_0.5Er_0.5)₂O₃ is similar to the one typical of Er₂O₃, with a total magnetic moment of 4.28(2) μ _B at both different magnetic sites; it is characterized by k  =  (0, 0, 0) and belongs to the magnetic $Ia\stackrel{¯<!--\; ??\; -->}{3}$ Shubnikov group. (paper)

[en] Highlights: ► A novel synthesis route is proposed and discussed to synthesize phase pure RuSr₂Gd_1.4Ce_0.6Cu₂O₁₀ samples. ► Phase purity is analyzed and discussed via structural, Raman and magnetic measurements. - Abstract: Two different synthetic routes to synthesize the magnetic superconductor RuSr₂Gd_1.4Ce_0.6Cu₂O_10−δ (Ru-1222) have been reported as an alternative method to the solid state reaction starting from the oxides of Ru, Gd, Ce, Cu and SrCO₃. The 1222-phase has been namely prepared by mixing and reacting proper amounts of: (a) the 1212-phase (RuSr₂GdCu₂O₈) with the mixed oxide Ce_0.6Gd_0.4O_1.8; (b) the 1212-phase with the separate oxides Gd₂O₃ and CeO₂. The possibility to obtain a pure Ru-1222 phase has been discussed and the effect of the different synthetic paths on the purity, structural and physical properties of the compound has been presented.

[en] GdSr₂RuCu₂O₈ has been synthesized using a solid state reaction and has been characterized from the structural and physical points of view. The samples exhibit the well-known superconducting and magnetic behavior; in addition, an orthorhombic modification of the GdSr₂RuCu₂O₈ lattice has been detected by both high resolution transmission electron microscopy (HRTEM) and x-ray powder diffraction (XRPD) analysis. Rietveld refinement of the XRPD data has been successfully performed in the orthorhombic Pmmm space group yielding an a₀xb₀xc₀(≅3 a₀) type cell, with octahedral RuO₆ polyhedra slightly distorted and rotated around c, b, and a