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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]

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]

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]

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]

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]