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γ1‐AuZn2.1 in the Au–Zn binary system has been synthesized and its structure analyzed by single‐crystal X‐ray diffraction. It crystallizes in the trigonal space group P31m (No. 157) with ∼227 atoms per unit cell and represents a 3a × 3a × c superstructure of rhombohedrally distorted γ‐Au5–xZn8+y. The structure is largely tetrahedrally closed packed. The formation of γ1‐AuZn2.1 can be understood within the framework of a Hume‐Rothery stabilization mechanism with a valence electron concentration of 1.68 e/a (valence electrons per atom). [ABSTRACT FROM AUTHOR]

Fe-Si electric steel is the most widely used soft magnetic material in electric machines and transformers. Increasing the silicon content from 3.2 wt.% to 6.5 wt.% brings about large improvement in the magnetic and electrical properties. However, 6.5 wt.% silicon steel is inherited with brittleness owing to the formation of B2 and D03 ordered phase. To obtain ductility in Fe-6.5wt.% silicon steel, the ordered phase has to be bypassed with methods like rapid cooling. In present paper, the effect of cooling rate on magnetic and mechanical properties of Fe-6.5wt.% silicon steel is studied by tuning the wheel speed during melt spinning process. The cooling rate significantly alters the ordering and microstructure, and thus the mechanical and magnetic properties. X-ray diffraction data shows that D03 ordering was fully suppressed at high wheel speeds but starts to nucleate at 10m/s and below, which correlates with the increase of Young’s modulus towards low wheel speeds as tested by nanoindentation. The grain sizes of the ribbons on the wheel side decrease with increasing wheel speeds, ranging from ∼100 μm at 1m/s to ∼8 μm at 30m/s, which lead to changes in coercivity. [ABSTRACT FROM AUTHOR]

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 R3 m 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. [ABSTRACT FROM AUTHOR]

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 R3 m 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. [ABSTRACT FROM AUTHOR]

ZrMnP and HfMnP single crystals are grown by a self-flux growth technique, and structural as well as temperature dependent magnetic and transport properties are studied. Both compounds have an orthorhombic crystal structure. ZrMnP and HfMnP are ferromagnetic with Curie temperatures around 370K and 320 K, respectively. The spontaneous magnetizations of ZrMnP and HfMnP are determined to be 1.9 μB/f.u. and 2.1 μB/f.u., respectively, at 50K. The magnetocaloric effect of ZrMnP in terms of entropy change (ΔS) is estimated to be -6.7 kJ m-3 K-1 around 369K. The easy axis of magnetization is [100] for both compounds, with a small anisotropy relative to the [010] axis. At 50 K, the anisotropy field along the [001] axis is ~4.6 T for ZrMnP and ~10T for HfMnP. Such large magnetic anisotropy is remarkable considering the absence of rare-earth elements in these compounds. The first principle calculation correctly predicts the magnetization and hard axis orientation for both compounds, and predicts the experimental HfMnP anisotropy field within 25%. More importantly, our calculations suggest that the large magnetic anisotropy comes primarily from the Mn atoms, suggesting that similarly large anisotropies may be found in other 3d transition metal compounds. [ABSTRACT FROM AUTHOR]

A series of pseudo-binary compounds MgZn2- xPdx (0.15 ≤ x ≤ 1.0) were synthesized and structurally characterized to understand the role of valence electron concentration ( vec) on the prototype Laves phase MgZn2 with Pd-substitution. Three distinctive phase regions were observed with respect to Pd content, all exhibiting fundamental Laves phase structures: 0.1 ≤ x ≤ 0.3 (MgNi2-type, hP24; MgZn1.80Pd0.20(2)), 0.4 ≤ x ≤ 0.6 (MgCu2-type, cF24; MgZn1.59Pd0.41(2)), and 0.62 ≤ x ≤ 0.8 (MgZn2-type, hP12: MgZn1.37Pd0.63(2)). Refinements from single-crystal X-ray diffraction indicated nearly statistical distributions of Pd and Zn atoms among the majority atom sites in these structures. Interestingly, the MgZn2-type structure re-emerges in MgZn2- xPd x at x ≈ 0.7 with the refined composition MgZn1.37(2)Pd0.63 and a c/ a ratio of 1.59 compared to 1.64 for binary MgZn2. Electronic structure calculations on a model ''MgZn1.25Pd0.75'' yielded a density of states (DOS) curve showing enhancement of a pseudogap at the Fermi level as a result of electronic stabilization due to the Pd addition. Moreover, integrated crystal orbital Hamilton population (ICOHP) values show significant increases of orbital interactions for (Zn,Pd)-(Zn,Pd) atom pairs within the majority atom substructure, i.e., within the Kagomé nets as well as between a Kagomé net and an apical site, from binary MgZn2 to the ternary ''MgZn1.25Pd0.75''. Multi-centered bonding is evident from electron localization function (ELF) plots for ''MgZn1.25Pd0.75'', an outcome which is in accordance with analysis of other Laves phases. [ABSTRACT FROM AUTHOR]

A series of pseudo-binary compounds MgZn2- xPdx (0.15 ≤ x ≤ 1.0) were synthesized and structurally characterized to understand the role of valence electron concentration ( vec) on the prototype Laves phase MgZn2 with Pd-substitution. Three distinctive phase regions were observed with respect to Pd content, all exhibiting fundamental Laves phase structures: 0.1 ≤ x ≤ 0.3 (MgNi2-type, hP24; MgZn1.80Pd0.20(2)), 0.4 ≤ x ≤ 0.6 (MgCu2-type, cF24; MgZn1.59Pd0.41(2)), and 0.62 ≤ x ≤ 0.8 (MgZn2-type, hP12: MgZn1.37Pd0.63(2)). Refinements from single-crystal X-ray diffraction indicated nearly statistical distributions of Pd and Zn atoms among the majority atom sites in these structures. Interestingly, the MgZn2-type structure re-emerges in MgZn2- xPd x at x ≈ 0.7 with the refined composition MgZn1.37(2)Pd0.63 and a c/ a ratio of 1.59 compared to 1.64 for binary MgZn2. Electronic structure calculations on a model ''MgZn1.25Pd0.75'' yielded a density of states (DOS) curve showing enhancement of a pseudogap at the Fermi level as a result of electronic stabilization due to the Pd addition. Moreover, integrated crystal orbital Hamilton population (ICOHP) values show significant increases of orbital interactions for (Zn,Pd)-(Zn,Pd) atom pairs within the majority atom substructure, i.e., within the Kagomé nets as well as between a Kagomé net and an apical site, from binary MgZn2 to the ternary ''MgZn1.25Pd0.75''. Multi-centered bonding is evident from electron localization function (ELF) plots for ''MgZn1.25Pd0.75'', an outcome which is in accordance with analysis of other Laves phases. [ABSTRACT FROM AUTHOR]

The results of crystallographic analysis, magnetic characterization, and theoretical assessment of ß-Mn-type Co-Zn intermetallics prepared using high-temperature methods are presented. These ß-Mn Co-Zn phases crystallize in the space group P4132 [Pearson symbol cP20; a = 6.3555(7)-6.3220(7)], and their stoichiometry may be expressed as Co8+xZn12-x [1.7(2) < x < 2.2(2)]. According to a combination of single-crystal X-ray diffraction, neutron powder diffraction, and scanning electron microscopy, atomic site occupancies establish clear preferences for Co atoms in the 8c sites and Zn atoms in the 12d sites, with all additional Co atoms replacing some Zn atoms, a result that can be rationalized by electronic structure calculations. Magnetic measurements and neutron powder diffraction of an equimolar Co:Zn sample confirm ferromagnetism in this phase with a Curie temperature of 420 K. Neutron powder diffraction and electronic structure calculations using the local spin density approximation indicate that the spontaneous magnetization of this phase arises exclusively from local moments at the Co atoms. Inspection of the atomic arrangements of Co8+xZn12-x reveals that the ß-Mn aristotype may be derived from an ordered defect, cubic Laves phase (MgCu2-type) structure. Structural optimization procedures using the Vienna ab initio simulation package (VASP) and starting from the undistorted, defect Laves phase structure achieved energy minimization at the observed ß-Mn structure type, a result that offers greater insight into the ß-Mn structure type and establishes a closer relationship with the corresponding a-Mn structure (cI58). [ABSTRACT FROM AUTHOR]

The region of the Au–Zn phase diagram encompassing γ-brass-type phases has been studied experimentally from 45 to 85 atom % Zn. The γ phases were obtained directly from the pure elements by heating to 680 °C in evacuated silica tubes, followed by annealing at 300 °C. Powder X-ray and single-crystal diffraction studies show that γ-"Au5Zn8" phases adopt a rhombohedrally distorted Cr5Al8 structure type rather than the cubic Cu5Zn8 type. The refined compositions from two single crystals extracted from the Zn- and Au-rich loadings are Au4.27(3)Zn8.26(3)⇔0.47 (I) and Au4.58(3)Zn8.12(3)⇔0.3 (II), respectively (⇔ = vacancy). These (I and II) refinements indicated both nonstatistical mixing of Au and Zn atoms as well as partially ordered vacancy distributions. The structures of these γ phases were solved in the acentric space group R3m (No. 160, Z = 6), and the observed lattice parameters from powder patterns were found to be a = 13.1029(6) and 13.1345(8) Å and c = 8.0410(4) and 8.1103(6) Å for crystals I and II, respectively. According to single-crystal refinements, the vacancies were found on the outer tetrahedron (OT) and octahedron (OH) of the 26-atom cluster. Single-crystal structural refinement clearly showed that the vacancy content per unit cell increases with increasing Zn, or valence-electron concentration. Electronic structure calculations, using the tight-binding linear muffin-tin orbital method with the atomic-sphere approximation (TB-LMTO-ASA) method, indicated the presence of a well-pronounced pseudogap at the Fermi level for "Au5Zn8" as the representative composition, an outcome that is consistent with the Hume–Rothery interpretation of γ brass. [ABSTRACT FROM AUTHOR]

Abstract: The crystal structure of the title compound has been determined by X-ray diffraction means. Pt29Zn49 forms a complex superstructure of a defective AlB2-type derivative of the order 58: a =279.0(1)pm, b =11895.2(4)pm, c =698.0(1)pm, space group Amm2, Z =2. Ordering of vacancies is accompanied by a particular distortion of defective graphite-like 63 nets consisting exclusively of Zn atoms. The ordering induces a modulation of the structure along a h of an AlB2-type structure with a periodicity of nearly 12nm. A mechanistic model is proposed elucidating how Pt29Zn49 evolves from the eutectoid decomposition of the inter-mediate high temperature precursor Pt7Zn12. [Copyright &y& Elsevier]

The constitution of the γ-phase field in the Pt&z.sbnd;Zn system was reinvestigated. The samples were prepared from the elements in sealed silica tubes at 1320 K followed by slow cooling to 970 K. Three structurally distinct γ-phases were identified by means of single crystal X-ray diffraction. The γ1- and γ1′-phase represent two structurally intimately related 2a×2a×2a superstructures of the ordinary γ-Pt2Zn10.75. Three crystal structures were refined from single crystal intensity data: γ1-Pt5.12Zn20.47 (F4¯3m, a=1809.1(1) pm, cF416-6.6, RF=0.043), γ1-Pt4.72Zn20.92 (F4¯3m, a=1812.8(2) pm, cF416-5.8, RF=0.034), and γ1′-Pt4.25Zn20.34 (F4¯3m, a=1814.0(1) pm, cF416-22.7, RF=0.054). The structures are discussed in terms of four symmetrically inequivalent 26 atom clusters each comprising inner tetrahedral (IT), outer tetrahedral (OT), octahedral (OH) and cuboctahedral (CO) positions. The homogeneity range of the γ1-phase extends between 18.4 and 20.0 at.% Pt, a range which encompasses the composition Pt5Zn21. Two symmetrically independent, ordered Pt4Zn22 clusters form the compositionally invariant part of the structure. Two complementary, partly disordered Pt6±δZn20−δ′ clusters account for the homogeneity range of the phase. They vary in composition due to mutual Pt/Zn substitution, vacancies at Zn sites, and partial positional disorder. The closely related phase γ1′-Pt4.25Zn20.34 is separated from the γ1-phase by a small miscibility gap which is indicated by isopiestic measurements and a discontinuous jump of the vacancy concentration. The melting point of the phases increases with rise of the Pt content: 1136(2) K (γ), 1238(5) K (γ1′) and 1251(3) K (γ1). The magnetic susceptibility is dominated by the core diamagnetism of the constituents. χmol was found to vary between −4.7×10−10 and −3.1×10−10 m3 mol−1. [Copyright &y& Elsevier]

The series of title compounds (0.15 ≤ x ≤ 1.0) is synthesized from the elements (Ta tubes, Ar, 750 °C, 18 h, followed by annealing at 400 °C for 5 d, 90-95% yields) and characterized by single crystal XRD and TB-LMTO-ASA electronic structure calculations to analyze the effect of valence electron concentration on MgZn2. [ABSTRACT FROM AUTHOR]

Single crystals of Fe 5 B 2 P were grown by self-flux growth technique. Structural and electrical and magnetic anisotropic properties are studied. The Curie temperature of Fe 5 B 2 P is determined to be 655±2 K. The saturation magnetization is determined to be 1.72 μ B / Fe at 2 K. The temperature variation of the anisotropy constant K 1 is determined for the first time, reaching ∼ 0.50 MJ / m 3 at 2 K, and it is comparable to that of hard ferrites. The saturation magnetization is found to be larger than the hard ferrites. The first principle calculations of saturation magnetization and anisotropy constant are found to be consistent with the experimental results. [ABSTRACT FROM AUTHOR]

Abstract: We present a detailed study of R 3Ni2−x Sn7 (R=La, Ce, Pr and Nd) single crystals by measurements of crystal structure, stoichiometry, temperature dependent magnetic susceptibility, magnetization, electrical resistivity, magnetoresistance and specific heat. This series forms with partial Ni occupancy with x varying from for R=La to for R=Nd. The electrical resistivity of this series follows metallic behavior at high temperatures. Determination of clear anisotropies as well as antiferromagnetic ordering temperatures for R 3Ni2−x Sn7 (R=Ce, Pr and Nd) have been made. For Pr3Ni1.56Sn7 and Nd3Ni1.34Sn7, multiple magnetic transitions take place upon cooling. Metamagnetic transitions in this family (R=Ce, Pr and Nd) were detected for applied magnetic fields below 70kOe. An phase diagram of Ce3Ni1.69Sn7 was assembled to shed light on its low field properties and to rule out possible quantum critical effects. [Copyright &y& Elsevier]

Formation energies of native defects in Bi2(TexSe3?x), with comparison to ideal Bi2Te2S, are calculated in density-functional theory to assess transport properties. Bi2Se3 is found to be n type for both Bi- and Se -rich growth conditions, while Bi2Te3 changes from n to p type going from Te- to Bi-rich conditions, as observed. Bi2Te2Se and Bi2Te2S are generally n type, explaining observed heavily doped n-type behavior in most samples. A (0/?) transition level at 16 meV above valence-band maximum for Bi on Te antisites in Bi2Te2Se is related to the observed thermally active transport gap causing a p-to-n transition at low temperature. Bi2(TexSe3?x) with x>2 are predicted to have high bulk resistivity due to effective carrier compensation when approaching the n-to-p crossover. Predicted behaviors are confirmed from characterization of our grown single crystals. [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]