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The crystal chemical features of the new series of compounds R6Mg23C with R = La-Sm or Gd and Ce6Mg23Z with Z = C, Si, Ge, Sn, Pb, P, As, or Sb have been studied by means of single-crystal and powder X-ray diffraction techniques. All phases crystallize with the cubic Zr6Zn23Si prototype (cF120, space group Fm3m, Z = 4), a filled variant of the Th6Mn23 structure. While no Th6Mn23-type binary rare earth-magnesium compound is known to exist, the addition of a third element Z (only 3 atom %), located into the octahedral cavity of the Th6Mn23 cell (Wyckoff site 4a), stabilizes this structural arrangement and makes possible the formation of the ternary R6Mg23Z compounds. The results of both structural and topological analyses as well as of LMTO electronic structure calculations show that the interstitial element plays a crucial role in the stability of these phases, forming a strongly bonded [R6Z] octahedral moiety spaced by zeolite cage-like [Mg45] clusters. Considering these two building units, the crystal structure of these apparently complex intermetallics can be simplified to the NaCl-type topology. Moreover, a structural relationship between RMg3 and R6Mg23C compounds has been unveiled; the latter can be described as substitutional derivatives of the former. The geometrical distortions and the consequent symmetry reduction that accompany this transformation are explicitly described by means of the Bärnighausen formalism within group theory. [ABSTRACT FROM AUTHOR]

Abstract: A study of the formation of Gd11M4In9 (M=Ni, Pd, Pt) and R11Ni4In9 (R=rare earth) compounds revealed a unique and peculiar property, which is to naturally crystallize in a bundle of self-assembled fibers when cooled from the melt. The fibers, which are nano- to millimeters in cross-section and ≈1–40mm long, grow unidirectionally along a temperature gradient. These compounds adopt the orthorhombic Nd11Pd4In9 structure type (oC48-Cmmm). This structure is layered, with slabs of R atoms alternating with slabs of Ni/In atoms along a short c-axis (much shorter than either the a- or b-axis). The growth direction of the fibers is along the crystallographic c-axis, orthogonal to the a–b plane. Two strong and short In–In bonds lie in the a–b plane, which are even shorter than in In metal. Integrated crystal orbital Hamilton population calculations show that the In–In bonds create isolated “R8Ni4In9” rods growing along the c-axis, with the In–In bonds being part of the rods. This appears to be an important factor explaining the microfibrous nature of these phases. Some physical properties have been measured on the Gd11Ni4In9 homolog. The compound orders ferrimagnetically at T C ≈88K, and at lower temperatures (46 and 10K), two other magnetic anomalies were observed, probably due to spin reorientations. As expected from the bonding features, the mechanical, magnetic and electrical properties are strongly anisotropic. [Copyright &y& Elsevier]

Abstract: Phases YbZn1− x Al x , YbZn2− x Al x and YbZn3− x Al x were studied by electron microprobe analysis and X-ray single crystal and powder methods. The compound YbZn0.8Al0.2 crystallizes with the CsCl-type, a=3.635(2)Å. Four phases were investigated by single crystal X-ray diffraction: YbZn0.996(6)Al1.004(6), MgNi2-type, P63/mmc, a=5.573(1), c=18.051(3)Å, Z=8, wR2=0.040 and YbZn0.88(3)Al1.12(3), MgCu2-type, , a=7.860(2)Å, Z=8, wR2=0.060, both showing mixed Zn/Al occupancy; YbZn2.50(1)Al0.50(1), CeNi3-type, P63/mmc, a=5.496(1), c=17.336(2)Å, Z=6, wR2=0.036 and YbZn1.92(2)Al1.08(2), PuNi3- or NbBe3-type, , a=5.499(1), c=26.134(5)Å, Z=9, wR2=0.053, where the zinc atoms are ordered in the CaCu5 segment, while share the sites with aluminium in the Laves phase segment. In the pseudobinary section YbZn2− x Al x four structures occur in sequence with increasing the electron concentration: CeCu2 or KHg2 (x=0–0.3), MgZn2 (x=0.33–0.54), MgNi2 (x=0.68–1.01) and MgCu2 (x=1.12–2). This sequence agrees with the results of first-principles calculations, already reported in the literature for other similar series. In the YbZn3− x Al x section CeNi3-type compounds occur with x=0.40–0.88 followed by PuNi3-type compounds with x=0.92–1.10. The stability ranges of these phases are related to the valence electron concentration. [Copyright &y& Elsevier]

Abstract: As part of a study of the Yb–Zn–Al system, this first article reports the synthesis and crystal structure of four compounds. The crystal structures were determined by single crystal diffractometer data for three of them: Yb3.36Zn30.94Al4.34, hexagonal, P6/mmm, , , , , with a structure derived from the SmZn11∼ type; Yb6.4Zn46.8Al3.4, hexagonal, P6/mmm, , , , , with its own structure; Yb12.4Zn96.8Al4.4, hexagonal, P63/mmc, , , , , with a structure derived from the U2Zn17 type. The structure of Yb3Zn17.7Al4.3, tetragonal, I41/amd, , , , related to the Ce3Zn22 type, was refined from powder data by the Rietveld method. The four structures belong to the same family, derived from the CaCu5 type by replacing totally or partially some Ca atoms with dumbbells of partner elements. All the structures show no order for the aluminium atoms, but they preferentially occupy the dumbbells sharing the sites with zinc. [Copyright &y& Elsevier]

A systematic study of the filled skutterudite system Sm y (Fe x Ni 1- x) 4 Sb 11.5 Sn 0.5 was carried out with the aim of investigating the effect of the partial substitution of Sb by Sn on the structural and thermoelectric properties of the material. The presence of Sn induces a shift of the p / n crossover toward lower values of x compared to the corresponding Sn-free system, as a consequence of the smaller number of electrons supplied. Moreover, a discontinuity at the p / n crossover is observed in the cell parameter and related structural features. The thermoelectric properties suggest lower thermal conductivity values in comparison to similar Sn-free skutterudite systems, resulting in higher ZT. This result highlights the significant role of Sn in creating new scattering centers able to affect the phonon transmission through the crystal lattice. [Display omitted] • Structural and thermoelectric properties of Smy(FexNi1-x)4Sb11.5Sn0.5 were studied. • The introduction of Sn moves the p/n crossover toward lower x. • A discontinuity occurs at the crossover in the cell parameter. • The introduction of Sn lowers phonon thermal conductivity and enhances ZT. • Thermoelectric properties are better than in the corresponding Sn-free system. [ABSTRACT FROM AUTHOR]

Mn doped (Cr 1-x Mn x) 2 AlC compounds constitute a family of MAX-phases of great interest due to the possibility of tuning the magnetic properties they possess. Their synthesis, however, is not an easy task. Two main issues make its preparation difficult. First is the strong tendency secondary phases have to segregate when manganese is added to the parent compound and, secondly, the resulting doping level which remains relatively low due to the poor incorporation of Mn atoms into the MAX-phase hexagonal structure [Cr 2 AlC-type]. In the present work the highest dopant concentration so far reported for bulk materials of 18.3 at.% Mn has been obtained through the exploitation of the arc-melting technique. At the same time, the use of the Cr 3 C 2 , as a precursor from the initial stage of the synthesis procedure, led to the preservation of the phase content in the Mn-doped samples. Finally, chemical post-treatment in acid solutions (HF, HCl) proved to be effective and helpful to dissolve the remaining secondary intermetallic phases; the final material resulting in a pure MAX-phase powder (>99 vol%). However, the doping level reached seems to be the limit for the arc fusion technique used; additional manganese no longer dissolves into the MAX-phase structure but tends to form some new Mn-based secondary phases, such as the perovskite Mn 3 AlC and the carbide MnC 2. After the chemical etching, pure MAX-phase powders can be compacted into bulk using spark plasma sintering technique. However, while this method is useful for the non-doped Cr 2 AlC, it needs further optimization for (Cr 1-x Mn x) 2 AlC as it leads to a partial decomposition of Mn-containing MAX-phase. [ABSTRACT FROM AUTHOR]

The title compounds are prepared by melting mixtures of the elements twice at 1100 °C followed by annealing (Ta crucible, 700 °C, 14 d). [ABSTRACT FROM AUTHOR]

The formation and crystal structure of the binary Cu3As phase have been re-investigated. Some physical properties were then measured on both single crystal and polycrystalline bulk. Cu3As melts congruently at 835 °C. At room temperature (RT), this compound has been found to crystallize in the hexagonal Cu3P prototype (hP24, P63cm) with lattice parameters: a = 7.1393(1) Å and c = 7.3113(1) Å, rather than in the anti HoH3-type (hP24, P–3c1) as indicated in literature. A small compositional range of 74.0–75.5 at.% Cu (26.0–24.5 at.% As) was found for samples synthesized at 300 and 400 °C; a corresponding slight understoichiometry is found in one out of the four Cu atomic sites, leading to the final refined composition Cu2.882(1)As. The present results disprove a change in the crystal structure above RT actually reported in the phase diagram (from γ' to γ on heating). Instead, below RT, at T = 243 K (−30 °C), a first-order structural transition to a trigonal low-temperature superstructure, LT-Cu3−xAs (hP72, P–3c1) has been found. The LT polymorph is metrically related to the RT one, having the c lattice parameter three times larger: a = 7.110(2) Å and c = 21.879(4) Å. Both the high- and low-temperature polymorphs are characterized by the presence of a tridimensional (3D) uncommon and rigid Cu sublattice of the lonsdaleite type (Cu atoms tetrahedrally bonded), which remains almost unaffected by the structural change(s), and characteristic layers of triangular 'Cu3As'-units (each hosting one As atom at the center, interconnected each other by sharing the three vertices). The first-order transition is then followed by an additional structural change when lowering the temperature, which induces doubling of also the lattice parameter a. Differential scanning calorimetry nicely detects the first low-temperature structural change occurring at T = 243 K, with an associated enthalpy difference, ΔH(TR), of approximately 2 J/g (0.53 kJ/mol). Low-temperature electrical resistivity shows a typical metallic behavior; clear anomalies are detected in correspondence to the solid-state transformations. The Seebeck coefficient, measured as a function of temperature, highlights a conduction of n-type. The temperature dependence of the magnetic susceptibility displays an overall constant diamagnetic response. [ABSTRACT FROM AUTHOR]

The crystallographic and transport properties of thin films fabricated by pulsed laser deposition and belonging to the Sm y (Fe x Ni1- x )4Sb12 filled skutterudite system were studied with the aim to unveil the effect exerted by temperature and duration of thermal treatments on structural and thermoelectric features. The importance of annealing treatments in Ar atmosphere up to 523 K was recognized, and the thermal treatment performed at 473 K for 3 h was selected as the most effective in improving the material properties. With respect to the corresponding bulk compositions, a significant enhancement in phase purity, as well as an increase in electrical conductivity and a drop in room temperature thermal conductivity, were observed in annealed films. The low thermal conductivity, in particular, can be deemed as deriving from the reduced dimensionality and the consequent substrate/film interfacial stress, coupled with the nanometric grain size. [ABSTRACT FROM AUTHOR]

During the investigation of the Cu-As-Sb ternary system, we identified the ternary intermetallic Cu 3−x (As,Sb) compound. Its crystal structure was solved and refined by single crystal and powder X-ray diffraction. While the binary Cu 3−x As and Cu 3−x Sb phases crystallize in the hexagonal Cu 3 P-type (hP 24, P 6 3 cm) and cubic anti-BiF 3 -type (cF 16, Fm 3 ¯ m), respectively, Cu 3−x (As,Sb) adopts the cubic Cu 6 AsSb prototype (cP 32, Pm 3 ‾ n). Crystallochemical reasons lead to the exclusion that its structure could be of the UH 3 -type. Cu 3−x (As,Sb) is isotypic with Cu 12−x TeSb 3 ; their crystal structure is a stuffed ternary derivative of the Cr 3 Si-type. SEM-EDX analyses reveal very large compositional ranges for this compound, mostly concerning the Sb/As ratio: 71.1−73.9 at.% Cu, 4.0−24.5 at.% As and 2.5−23.5 at.% Sb, corresponding to about Cu 2.5-2.8 As 0.23-0.98 Sb 0.23-0.92 (x = 0.2−0.5). The lattice parameter and, consequently, the unit cell volume regularly expand while increasing the Sb/As compositional ratio: a ≈ 7.47 Å for Cu 3−x As 0.75 Sb 0.25 , a ≈ 7.65 Å for Cu 3−x As 0.25 Sb 0.75 (averaged values). Cu 3−x (As,Sb) forms either by a peritectic reaction for As-rich compositions, or congruently for the equiatomic Sb/As and Sb-rich compositions. The decomposition- or melting-temperature values decrease as a function of the Sb/As compositional ratio [ e.g. peritectic at 710 °C for Cu 3−x As 0.75 Sb 0.25 (Cu 72 As 21 Sb 7), congruent melting at 690 °C for Cu 3−x As 0.50 Sb 0.50 (Cu 72 As 14 Sb 14), and at 675 °C for Cu 3−x As 0.25 Sb 0.75 (Cu 72 As 7 Sb 21)]. Physical properties (electrical resistivity and magnetic susceptibility) indicate that Cu 3−x (As,Sb) behaves as a good metal with electrical resistivity decreasing as the Sb/As compositional ratio increases; a peculiar anomaly in the electrical resistivity behavior (heavy-fermions like) was observed at low temperature, the origin of which needs further investigation. The compound is a standard diamagnet. • new ternary intermetallic Cu 3−x (As,Sb) compound identified. • first isotypic intermetallic compound crystallizing with the ternary Cu 9.1 TeSb 3 aristotype. • electrical resistivity indicate a good metal. • peculiar anomaly in electrical resistivity behavior observed at low temperature. • the intermetallic Cu 3−x (As,Sb) compound is a standard diamagnet. [ABSTRACT FROM AUTHOR]

The central part of the La–Ni–Si system has been investigated at 800 °C by means of single crystal X-ray diffraction, microscopy and analytical microprobe techniques. The result led to the identification of four new metal-rich silicides: LaNi2Si (R3¯m, a = 4.0263(3) Å, c = 15.066(2) Å, Z = 3), La2Ni3Si2 (P21/c, a = 6.8789(7) Å, b = 6.2167(3) Å, c = 12.214(1) Å, β = 90.92(1), Z = 4), La3Ni3Si2 (Pnma, a = 7.501(2) Å, b = 14.316(4) Å, c = 6.149(2) Å, Z = 4), La6Ni7Si4 (Pbcm, a = 6.066(1) Å, b = 7.488(1) Å, c = 29.682(5) Å, Z = 4). LaNi2Si belongs to the SrCu2Ga structure type, which is not represented among silicides, while La2Ni3Si2 crystallizes in its own structure type. Both compounds feature layered polyanionic motifs consisting of Ni and Si, which are separated by La. Instead, La6Ni7Si4 and La3Ni3Si2 are characterized by polyanionic networks. The former compound belongs to the Pr6Ni7Si4 structure type, with only two other representatives (Ce and Nd); the latter has been observed only with Rh and Ir. The two structures reveal close structural relationships having multiple identical slabs. Tight-binding electronic structure calculations by linear muffin-tin-orbital methods were performed for LaNi2Si, La2Ni3Si2 and La3Ni3Si2 to gain insights into their structure–bonding relationships. Their band structures suggest a metallic character for all compounds. The overall crystal orbital Hamilton populations are dominated by polar Ni–Si bonds, though homoatomic Ni–Ni and La–Ni(Si) bond contributions are not negligible. The variety of bonding patterns may serve as a logical explanation for the number of discovered compounds in this system as well as for the diversity of the observed structures. [ABSTRACT FROM AUTHOR]

The discovery of new superconducting materials represents a complementary and crucial tile to shed light on the mechanism controlling the phenomenon of superconductivity. During the search for new superconducting materials, we discovered a new series of intermetallic compounds with the general composition RZn 2−x Sn 2 (R = La, Ce, Pr, Nd). Their formation and crystal structure have been investigated. The Zn content decreases along the series from ≈ 1.50 in LaZn 1.50(1) Sn 1.98(2) to ≈ 1.32 in NdZn 1.321(8) Sn 2.01(2) , due to the partial occupation of one of the two Zn sites [the Zn1 (2 c) site, which from ≈ 50% in the La compound drops to ≈ 42%, ≈ 37% and ≈ 32% in the Ce, Pr and Nd compounds, respectively]. Both the Zn occupation factor and unit cell volume follow the lanthanide contraction. No such compound has been observed with Sm. AC and DC magnetic susceptibility and transport measurements revealed LaZn 1.5 Sn 2 to undergo a sharp superconducting transition at T c = 5.5 K. In order to search for further possible superconductive homologues, the lanthanum substituted phases La(Zn,T) 2–x Sn 2 (T = Ti, Mn, Fe, Co, Ni, Cu, Pd, Ag, Pt, Au, Cd; x ≈ 0.5) were also prepared. The crystal structure of the ternary compounds is a disordered defective derivative of the tetragonal CaBe 2 Ge 2 -type (tP 10, P 4 /nmm), with a partially occupied Zn Wyckoff site and a disordered Sn position. Three related isostructural series, corresponding to three new prototypes, have been identified; they all contain conventional checkered pyramidal layers characteristic of the archetype. The magnetic and transport properties have been measured for some of these substituted quaternary La compounds and we found that superconductivity is preserved in them but in the orthorhombic compounds or when T was a magnetic transition metal (e.g. , Ni or Mn). A slight decrease in T c down to about 4.0 K was detected as a result of the Zn by T atomic substitution. • New rare-earth intermetallics RZn 2−x Sn 2 (R = La-Nd) and La(Zn,T) 2–x Sn 2 were discovered and studied. • Crystal structure is a disordered defective derivative of tetragonal CaBe 2 Ge 2 -type. • Three new related orthorhombic prototypes were identified. • LaZn 1.5 Sn 2 is a superconductor with T c = 5.5 K. • Superconductivity is preserved in most of the pseudo-ternary substituted La(Zn,T) 2–x Sn 2. [ABSTRACT FROM AUTHOR]

A complex optimization of the arc melting synthetic approach was performed to enhance the phase purity of Cr 2 AlC MAX-phase in the bulk form. Optimization steps included the initial ratio of 2Cr: xAl: 1C, variation through a change in Al content (i.e. x ranging from 1 to 1.5), tuning duration of the post-annealing thermal treatment and adjustment of the melting chamber pressure. The use of Cr 3 C 2 as a precursor in place of Cr and C mixture has also been tried. It was found that Cr 2 AlC MAX-phase forms as the predominant phase when a stoichiometric ratio 2Cr: 1.3Al: 1C is used. By keeping this stoichiometry constant, the melting chamber pressure was then adjusted to further improve the phase purity of the samples. It has been established that the use of Cr 3 C 2 is not an appropriate way to improve sample purity and promote homogeneity in the carbon distribution. The establishment of an optimized arc fusion protocol for parental Cr 2 AlC is a necessity for further successful mass synthesis of the substituted (Cr 1-x Mn x) 2 AlC MAX-phase. [ABSTRACT FROM AUTHOR]

We report the synthesis of new alloys of the composition RCu4Be derived by substituting Be for Cu in the well known parent binary RCu5 (R = rare earth) compounds. For R = Nd, Sm, Gd, Tb, Dy, Ho, and Y, the as cast RCu4Be compounds form in the hexagonal CaCu5 type structure. ErCu4Be and TmCu4Be adopt the cubic AuBe5 type symmetry like their parent compounds. The magnetic properties of RCu4Be compounds have been probed by magnetization, electrical resistivity, and heat capacity measured down to 1.8 K. With the exception of TmCu4Be and nonmagnetic YCu4Be the compounds order magnetically with the highest transition temperature of 56 K observed in GdCu4Be. The nature of the magnetic ordering is predominantly ferromagnetic though the corresponding RCu5 compounds are mostly antiferromagnetic with relatively low magnetic ordering temperatures. The thermal variation of the electrical resistivity is in conformity with their metallic nature and reflects the transition into the magnetically ordered state. The evidence for the bulk nature of the magnetic ordering is further elucidated from the heat capacity data which show anomalies at the magnetic transition. [ABSTRACT FROM AUTHOR]

Magnetic compounds possessing an intrinsic combination of near-zero magnetization with high magnetic anisotropy are highly desirable for spinronic applications and memory recording. A comprehensive study of Sm 7 Pd 3 binary compound uncovered a unique combination of strong magnetoelastic behavior, very low net magnetization, and exceptionally high magnetic coercivity. The temperature-dependent X-ray synchrotron powder diffraction study indicates the abrupt changes in the compound's lattice parameters at the magnetic ordering temperature of T C =169 K, although the crystal structure remains non-centrosymmetric hexagonal Th 7 Fe 3 -type down to 6 K. Density functional theory calculations confirm high intrinsic magnetocrystalline anisotropy of Sm 7 Pd 3 , which explains the extremely large coercivity of the polycrystalline sample, up to H cr = 130 kOe at 2 K. This discovery brings to life a novel class of highly anisotropic materials that are distinctly different from known spintronic materials, making them interesting future systems for magnetic memory research. [Display omitted] [ABSTRACT FROM AUTHOR]

The magnetic properties, the crystal and the magnetic structures of the new 1: 1 RCo 1−x Ni x phase formed by R = Tb, Dy and Ho, have been studied for x = 0.4 and 0.5 by means of physical property measurements, neutron and X-ray (from both laboratory and synchrotron) diffraction methods. These compounds crystallize in the tetragonal MoB structure type (tI 16, I 4 1 /amd) at room temperature, with no ordered arrangement of Co/Ni atoms on the 8 e Wyckoff site available for the transition element. Both the lattice parameters a and c (and unit cell volume, V obs) decrease from Tb to Ho, with a and c following a linear and a quadratic trend, respectively. A magnetic phase transition is detected by heat capacity and magnetization data for TbCo 0.6 Ni 0.4 at about 85 K. Similar transitions appear in DyCo 0.6 Ni 0.4 and HoCo 0.6 Ni 0.4 at 49 K and 27 K, respectively. These T C well follow the de Gennes factor along the lanthanide series. Neutron diffraction shows for the Tb- and Ho-compounds that strongly ferromagnetic structures characterized by a k = 0 magnetic propagation vector are formed on two different rare earth sublattices which are canted to each other. Only in the Tb-containing phases the magnetic transition leads to a symmetry reduction from tetragonal I 4 1 / amd to at least monoclinic I 2/ a. Magnetic symmetry analysis is used to argue that the presence of a magnetic moment component along the original tetragonal axis should be at the origin of this magneto-structural transition in the Tb-compounds with a possible further symmetry lowering. [Display omitted] • Crystal and magnetic structures of new RCo 1−x Ni x (R = Tb, Dy, Ho; x = 0.4, 0.5) intermetallics. • RCo 1−x Ni x (R = Tb, Dy, Ho; x = 0.4, 0.5) adopts the tetragonal MoB-type; no Co/Ni ordering. • RCo 1−x Ni x (R = Tb, Dy, Ho; x = 0.4, 0.5) orders ferromagnetically at T C = 85, 49, 27, 25 K. • Tb and Ho phases show commensurable magnetic structure with moment on the a-b plane. • Tetragonal-to-monoclinic magnetostructural transition takes place in Tb phases at T C. [ABSTRACT FROM AUTHOR]

Twenty new ternary representatives of the Gd14Ag51 structure type have been synthesized within the R-Au-M family (R = Y, La–Nd, Sm–Tb, Ho, Er, Yb, Lu; M = Al, Ga, Ge, In, Sn, Sb, Bi) using solid state synthesis techniques. The list of post transition metals (M) involved in the formation of this type of structure could be augmented by five new representatives. All compounds crystallize in the hexagonal space group P6/m (#175) with the unit cell ranges of a = 12.3136(2)–12.918(1) Å and c = 8.9967(3)–9.385(1) Å, and incorporate different degrees of Au/M mixing. The involvement of the post transition element in the structure varies from one to another compound both qualitatively and quantitatively. A rather significant phase width can be expected for the majority of compounds, however, not without exclusions. The distribution of the post transition metals within the structure has been analyzed via single crystal X-ray diffraction. While the positional disorder of one near-origin Au position is expectable for all compounds due to steric reasons, two specimens show an obvious deviation from the others including another Au position split along the c axis. Possible factors affecting this behavior are discussed. [ABSTRACT FROM AUTHOR]

The binary GdNi adopting the orthorhombic CrB-type (oS 8, Cmcm) dissolves up to 21 at% Co (GdCo 0.42 Ni 0.58), but when the Co content reaches 23.7 at% the crystal structure of the GdCo x Ni 1−x phase changes from the orthorhombic CrB-type to the tetragonal MoB-type (tI 16, I 4 1 /amd). The latter remains stable between 23.7 and 36.0 at% Co (0.47 ≤ x Co ≤ 0.72), and there is a two-phase region compositional gap of ≈ 2.5 at% Co between the two structures. One of the two 8 e sites available in the MoB-type structure is filled by Gd atoms, while Co and Ni atoms are randomly occupying the other 8 e site. The lattice parameter a increases from 3.9485(1) Å to 3.9591(1) Å, while c decreases from 21.3286(1) Å to 21.2404(1) Å as x Co increases, both following a quadratic trend. As a result, the unit cell volume increases from 332.53(2) Å3 to 332.93(2) Å3 for, respectively, the Co-poor (GdCo 0.47 Ni 0.53) and the Co-rich (GdCo 0.72 Ni 0.28) sides of the solid solution, also following a quadratic trend with a negative deviation of the Zen's law. The title compound becomes ferromagnetic with T C increasing linearly from 150 K for GdCo 0.50 Ni 0.50 to 171 K for GdCo 0.70 Ni 0.30 ; linear interpolation leads to T C = 127 K and 174 K for the two ends of the solid solution with x Co = 0.47 and 0.72, respectively. The magnetic susceptibility follows the Curie-Weiss law, indicating a trivalent state of Gd ions, with an effective magnetic moment slightly increasing with the Co content. The magnetocaloric effect, calculated in terms of the isothermal magnetic entropy change, decreases slightly as x Co increases, remaining large in the range 127–174 K. [Display omitted] • GdCo x Ni 1−x (0.47 ≤ x ≤ 0.72) is a new intermetallic compound in the Gd-Co-Ni system. • GdCo x Ni 1−x adopts the tetragonal MoB-type and forms for 0.47 ≤ x ≤ 0.72. • MoB-type GdCo x Ni 1−x (0.47 ≤ x ≤ 0.72) is soft ferromagnet with T C ranging from 127 to 174 K. • MoB-type GdCo x Ni 1−x shows a relatively large magnetocaloric effect (120–180 K range). • MoB-type GdCo x Ni 1−x is a new promising magnetic refrigerant material. [ABSTRACT FROM AUTHOR]

The phases reported in the literature as "R2Pd3" (R = rare earth element) have been reinvestigated. The exact stoichiometric composition of this series of compounds, which form for R = Sc, Y, and from Gd to Lu, including Yb, was found to be R3Pd5. All of them crystallize in the orthorhombic Pu3Pd5 structure type (oS32-Cmcm). The crystal structure has been refined from both single crystal (for Tb3Pd5) and powder X-ray diffraction data (for Tb3Pd5, Ho3Pd5, and Tm3Pd5). These compounds represent the first example of a binary phase formed by R and Pd adopting the Pu3Pd5-type featuring two crystallographic nonequivalent sites for the R atoms in the unit cell (the Wyckoff sites 4c and 8e). The variation of the lattice parameters and unit cell volume along the series strictly follows the trend of the lanthanide contraction. An extrapolation of the volume contraction versus the R3+ ionic radius gives an atomic volume of 29.74 ų for Yb in the hypothetical trivalent metallic state (under normal conditions). The formation temperatures and mechanisms, a peritectic reaction, and stability ranges have also been investigated. It turns out that Gd3Pd5 is a high temperature phase; it was not possible to quench this compound as a metastable phase, at room temperature, to be measured. In the light of our results, most of the R-Pd phase diagrams need to be revised. The magnetization, heat capacity, and electrical resistivity have been measured for Tb3Pd5, Dy3Pd5, Ho3Pd5, and Er3Pd5. They order antiferromagnetically at low temperatures, each undergoing two transitions, TN1 and TN2 (with TN1 going from 13.5 to 5.1 K and TN2 going from 6.5 to 3.6 K, respectively for Tb and Ho compounds). From our data we cannot distinguish whether the two rare earth sublattices sequentially order magnetically at TN1 and TN2, respectively, or whether they are simultaneously involved in both transitions. The electronic structure calculations predict antiferromagnetic ordering also for Gd3Pd5. Y3Pd5 is a Pauli paramagnet. [ABSTRACT FROM AUTHOR]

A series of isotypes of ternary rare earth element-gold-tetrel intermetallic compounds have been synthesized, and their structures and properties have been characterized. R3Au7Sn3 (R = Y, La-Nd, Sm, Gd-Tm, Lu) crystallize with the hexagonal Gd3Au7Sn3 prototype (Pearson symbol hP26; P63/m, a = 8.110-8.372 Å, c = 9.351-9.609 Å, Vcell = 532.7-583.3 ų, Z = 2), an ordered variant of the Cu10Sn3-type. Their structures are built up by GdPt2Sn-type layers, which feature edge-sharing Sn@Au6 trigonal antiprisms connected by trigonal R3 groups. Additional insertion of gold atoms leads to the formation of new homoatomic Au clusters, Au@Au6; alternatively, the structure can be considered as a superstructural polyhedral packing of the ZrBeSi-type. The magnetization, heat capacity, and electrical resistivity have been measured for R3Au7Sn3 (R = Ce, Pr, Nd, and Tb). All four compounds order antiferromagnetically with the highest TN of 13 K for Tb3Au7Sn3. In Ce3Au7Sn3, which has a TN of 2.9 K, the heat capacity and electrical resistivity data in zero and applied fields indicate the presence of Kondo interaction. The coefficient of the linear term in the electronic heat capacity, γ, derived from the heat capacity data below 0.5 K is 211 mJ/Ce mol K², suggesting strong electronic correlations due to the Kondo interaction. The electronic structure calculations based on the projector augmented wave method for particular representatives of the series suggest different tendencies of the localized R-4f atomic orbitals (AOs) to hybridize with the valence states. LMTO-based bonding analysis on the nonmagnetic La3Au7Sn3 indicates that the integrated crystal orbital Hamilton populations are dominated by the heteroatomic Au-Sn contacts; however, contributions from La-Au and La-Sn separations are significant, both together exceeding 40% in the overall bonding. Homoatomic Au-Au interactions are evident for the Au@Au6 units, but, despite of the high atomic concentration of Au in the compound, they do not dominate the entire bonding picture. [ABSTRACT FROM AUTHOR]

We have investigated the effects of the isovalent ruthenium substitution in LaFe [ABSTRACT FROM AUTHOR]

Single crystals of the quaternary europium com-pounds EuRhAl4Si2 and EuIrAl4Si2 were synthesized by using the Al--Si binary eutectic as a flux. The structure of the two quaternary compounds has been refined by single crystal X-ray diffraction. Both compounds are stoichiometric and adopt an ordered derivative of the ternary KCu4S3 structure type (tetragonal tP8, P4/mmm). The two compounds reported here represent the first example of a quaternary and truly stoichiometric 1:1:4:2 phase crystallizing with this structure type. In light of our present results, the structure of the BaMg4Si3 compound given in literature as representing a new prototype is actually isotypic with the KCu4S3 structure. Local spin density approximation including the Hubbard U parameter (LSDA + U) calculations show that Eu ions are in the divalent state, with a significant hybridization between the Eu 5d, Rh (Ir) 4d (5d), Si 3p and Al 3p states. Magnetic susceptibility measured along the [001] direction confirms the divalent nature of the Eu ions in EuRhAl4Si2 and EuIrAl4Si2, which order magnetically near ~11 and ~15 K, respectively. [ABSTRACT FROM AUTHOR]

We present a systematic study of the superconducting properties of high quality V3Si thin films, grown by high vacuum pulsed laser deposition from a stoichiometric target, a technique never reported in literature for this compound. By changing both the substrate (crystal structure and orientation) and the deposition conditions (substrate temperature, target-substrate distance, laser frequency and pulse energy) the critical temperature and the resistivity values of the samples have been finely tuned. Best results (TC - 16.1 K and Residual Resistivity Ratio RRR = 8.5) are obtained for deposition temperatures higher than 12000 C on both LaAlO3 and MgO substrates. All the samples are polycrystalline, that however does not affect the good quality of the transport properties. The possibility of multiband superconductivity in this com- pound is investigated, probing as a function of temperature: (i) the critical field up to 28 T using voltamperometric measurements, and (ii) the superfluid density via magnetic penetration depth measurements with a single coil inductive technique operating in the MHz region. [ABSTRACT FROM AUTHOR]

Filled skutterudites are currently studied as promising thermoelectric materials due to their high power factor and low thermal conductivity. The latter property, in particular, can be enhanced by adding scattering centers, such as the ones deriving from low dimensionality and the presence of interfaces. This work reports on the synthesis and characterization of thin films belonging to the Smy(FexNi1−x)4Sb12-filled skutterudite system. Films were deposited under vacuum conditions by the pulsed laser deposition (PLD) method on fused silica substrates, and the deposition temperature was varied. The effect of the annealing process was studied by subjecting a set of films to a thermal treatment for 1 h at 423 K. Electrical conductivity σ and Seebeck coefficient S were acquired by the four-probe method using a ZEM-3 apparatus performing cycles in the 348–523 K temperature range, recording both heating and cooling processes. Films deposited at room temperature required three cycles up to 523 K before being stabilized, thus revealing the importance of a proper annealing process in order to obtain reliable physical data. XRD analyses confirm the previous result, as only annealed films present a highly crystalline skutterudite not accompanied by extra phases. The power factor of annealed films is shown to be lower than in the corresponding bulk samples due to the lower Seebeck coefficients occurring in films. Room temperature thermal conductivity, on the contrary, shows values comparable to the ones of doubly doped bulk samples, thus highlighting the positive effect of interfaces on the introduction of scattering centers, and therefore on the reduction of thermal conductivity. [ABSTRACT FROM AUTHOR]

Single crystals of the title compounds are prepared from the elements using an eutectic Al-Si mixture as a flux (alumina crucible, 1100 °C, 24 h). [ABSTRACT FROM AUTHOR]