Synthesis, characterization, and phase relations of Zinc-Rich phases in the binary systems Platinum-Zinc and Nickel-Zinc

Synthesis, characterization, and phase relations of Zinc-Rich phases in the binary systems Platinum-Zinc and Nickel-Zinc

Synthesis, characterization, and phase relations of Zinc-Rich phases in the binary systems Platinum-Zinc and Nickel-Zinc

Synthesis, characterization, and phase relations of Zinc-Rich phases in the binary systems Platinum-Zinc and Nickel-Zinc

Structural and ferromagnetic properties of an orthorhombic phase of MnBi stabilized with Rh additions

The article addresses the possibility of alloy elements in MnBi which may modify the thermodynamic stability of the NiAs-type structure without significantly degrading the magnetic properties. The addition of small amounts of Rh and Mn provides an improvement in the thermal stability with some degradation of the magnetic properties. The small amounts of Rh and Mn additions in MnBi stabilize an orthorhombic phase whose structural and magnetic properties are closely related to the ones of the previously reported high-temperature phase of MnBi (HT~MnBi). To date, the properties of the HT~MnBi, which is stable between $613$ and $719$~K, have not been studied in detail because of its transformation to the stable low-temperature MnBi (LT~MnBi), making measurements near and below its Curie temperature difficult. The Rh-stabilized MnBi with chemical formula Mn$_{1.0625-x}$Rh$_{x}$Bi [$x=0.02(1)$] adopts a new superstructure of the NiAs/Ni$_2$In structure family. It is ferromagnetic below a Curie temperature of $416$~K. The critical exponents of the ferromagnetic transition are not of the mean-field type but are closer to those associated with the Ising model in three dimensions. The magnetic anisotropy is uniaxial; the anisotropy energy is rather large, and it does not increase when raising the temperature, contrary to what happens in LT~MnBi. The saturation magnetization is approximately $3$~$\mu_B$/f.u. at low temperatures. While this exact composition may not be application ready, it does show that alloying is a viable route to modifying the stability of this class of rare-earth-free magnet alloys.Comment: 9 pages, 10 figure

Hydrostatic pressure study of single-crystalline UNi0.5Sb2

We studied single-crystals of the antiferromagnetic compound UNi0.5Sb2 (TN ~ 161 K) by means of measurements of magnetic susceptibility (chi), specific heat (Cp), and electrical resistivity (rho) at ambient pressure, and resistivity under hydrostatic pressures up to 20 kbar, in the temperature range from 1.9 to 300 K. The thermal coefficient of the electrical resistivity (drho/dT) changes drastically from positive below TN to negative above, reflecting the loss of spin-disorder scattering in the ordered phase. Two small features in the rho vs T data centered near 40 and 85 K correlate well in temperature with features in the magnetic susceptibility and are consistent with other data in the literature. These features are quite hysteretic in temperature, i.e., the difference between the warming and cooling cycles are about 10 and 6 K, respectively. The effect of pressure is to raise TN at the approximate rate of 0.76 K/kbar, while progressively suppressing the amplitude of the small features in rho vs T at lower temperatures and increasing the thermal hysteresis.Comment: 9 pages, 3 figues, 2007-mmm conferenc

Liquid/Single Crystal Structure Analysis: Synthesis and Characterization of a Trimethylsilyl Derived Rod Shaped Mesogen

4-[4’-Cyanophenoxy-carbonyl-phenyl-4-(trimethylsilyl)ethynyl]benzoate a rod shaped liquid crystal (SmA) is synthesized and characterized. The single-crystals were grown in triclinic crystal system in the space group of Pi - with unit cell parameters a = 5.9577(2) Å, b = 8.0398(3) Å, c = 25.8842(9) Å, a = 86.096(2)o , ß = 89.912(2)o , ? = 2.919(2)o , Z = 2, and V = 1182.16(7). The crystal structure is stabilized by C–H···O intra-molecular interactions. Further, the structure also involves C–H···p interactions and weak p–p stacking interactions [centroid–centroid separation = 3.806 (3) Å

Pd2.28(1)Zn10.37(1)Al0.35(1), a ternary γ-brass-type structure

Palladium zinc aluminium (2.28/10.37/0.35), Pd2.28(1)Zn10.37(1)Al0.35(1), represents the upper limit of Al substitution into the parent cubic γ-brass Pd2+xZn11−x. The structure can be described in terms of a 26-atom cluster consisting of an inner tetra­hedron (IT), an outer tetra­hedron (OT), an octa­hedron (OH) and a cubocta­hedron (CO), with the substituted Al atoms partially occupying the IT (.3m) and CO (..m) sites

Crystal structure, homogeneity range and electronic structure of rhombohedral γ-Mn5Al8

The γ-region of the Mn–Al phase diagram between 45 and 70 at.% Al was re-investigated by a combination of powder and single crystal X-ray diffraction as well as EDS analysis to establish the distribution of Mn and Al atoms. Single crystals of γ-Mn5–x Al8+x were grown using Sn-flux at 650 °C. The crystal structure, atomic coordinates and site occupancy parameters of γ-Mn5−x Al8+x phases were refined from single crystal X-ray data. The γ-Mn5-x Al8+x phase adopts the rhombohedral Cr5Al8-type structure rather than a cubic γ-brass structure. The refined compositions from two crystals extracted from the Al-rich and Mn-rich sides are, respectively, Mn4.76Al8.24(2) (I) and Mn6.32Al6.68(2) (II). The structure was refined in the acentric R3m space group (No.160, Z=6), in order to compare with other reported rhombohedral γ-brasses. In addition, according to X-ray powder diffraction analysis, at the Al-rich side the γ-phase coexists with LT–Mn4Al11 and, at the Mn-rich side, with a hitherto unknown phase. The refined lattice parameters from powder patterns fall in the range a=12.6814(7)−12.6012(5) Å and c=7.9444(2)−7.9311(2) Å from Al-rich to Mn-rich loadings, and the corresponding rhombohedral angles distorted from a pseudo-cubic cell were found to be 89.1(1)°−88.9(1)°. Magnetic susceptibility and magnetization studies of Mn4.92Al8.08(2) are consistent with moment bearing Mn and suggest a spin glass state below 27 K. Tight-binding electronic structure calculations (LMTO-ASA with LSDA) showed that the calculated Fermi level for γ-“Mn5Al8” falls within a pseudogap of the density of states, a result which is in accordance with a Hume-Rothery stabilization mechanism γ-brass type phases