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Single crystals of CaMgSi were produced using the metal flux synthesis method in a Mg/Al 1:1 mixture. The large rod-shaped crystals measure up to 7 mm in length. This phase crystallizes with the orthorhombic TiNiSi structure type (space group Pnma; a = 7.4752(2) Å, b = 4.42720(10) Å, c = 8.3149(2) Å; R 1 = 0.021). Despite its relationship to semiconducting Zintl phases Mg2Si and Ca2Si, CaMgSi is metallic at room temperature; this produces a positive (∼160 ppm) 29Si MAS NMR chemical shift and is supported by DOS calculations. A metal to semimetal electronic transition at around 50 K is evident in the resistivity, magnetic susceptibility, and electron paramagnetic resonance measurements. Low temperature powder X-ray diffraction data indicates that a structural distortion accompanies this transition. The electronic heat capacity coefficient (0.4695 mJ/mol·K2) determined from low temperature heat capacity data supports the designation of CaMgSi as a semimetal at low temperature. The hydrogen storage capacity of this phase is negligible (≤0.5 wt % hydrogen), although exposure to hydrogen does destabilize the structure, inducing decomposition at 500 °C.

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Reactions of europium and tin in 1:1 Mg/Al mixed flux produce large crystals of EuMgSn. This phase crystallizes with the TiNiSi structure type in orthorhombic space group Pnma (a = 8.0849(7) Å, b = 4.8517(4) Å, c = 8.7504(8) Å, Z = 4, R1 = 0.0137). The crystal structure features europium cations positioned between puckered hexagonal layers comprised of magnesium and tin atoms. Magnetic susceptibility measurements indicate the europium in this phase is divalent, which suggests that the compound is possibly valence-balanced as Eu(2+)Mg(2+)Sn(4-). However, EuMgSn is a metal as indicated by density of states calculations and electrical resistivity behavior. This phase exhibits antiferromagnetic ordering at T(N) = 10.9 K at low field (100 G) and the ordering temperature decreases when a higher magnetic field is applied. ac magnetization and field dependence of resistivity at 4.2 K reveal that there is a spin reorientation at 2 T, in agreement with the metamagnetic transition shown in the dc magnetization versus field data. Temperature dependence of resistivity at 2.5 T indicates that EuMgSn has a large magnetoresistance up to -30% near its magnetic ordering temperature.

The nitride-hydride Ba3CrN3H was obtained in single crystalline form using flux growth techniques based on alkaline earth metals. Ba3CrN3H crystallizes in the hexagonal space group P63/m (Nr 176), with the lattice parameters a = 8.0270(2) Å and c = 5.6240(1) Å, Z=2. The structure comprises [CrN3] 5trigonal planar units, and [HBa6] 11+ octahedral units. The presence of anionic hydrogen in the structure has been verified by 1 H NMR experiments. DFT calculations show that the addition of hydrogen increases the stability of the phase versus Ba3CrN3. The two d-electrons of Cr 4+ are located in the non-bonding dz 2 orbital, rendering Ba3CrN3H non-magnetic and insulating.

We compare the superconducting phase-diagram under high magnetic fields (up to H = 45 T) of Fe1+ySe0.4Te0.6 single crystals originally grown by the Bridgman-Stockbarger (BRST) technique, which were annealed to display narrow superconducting transitions and the optimal transition temperature Tc 14 K, with the diagram for samples of similar stoichiometry grown by the travelingsolvent floating-zone technique as well as with the phase-diagram reported for crystals grown by a self-flux method. We find that the so-annealed samples tend to display higher ratios Hc2/Tc, particularly for fields applied along the inter-planar direction, where the upper critical field Hc2(T ) exhibits a pronounced downward curvature followed by saturation at lower temperatures T . This last observation is consistent with previous studies indicating that this system is Pauli limited. An analysis of our Hc2(T ) data using a multiband theory suggests the emergence of the Fulde-Ferrel-Larkin-Ovchnikov state at low temperatures. A detailed structural x-ray analysis, reveals no impurity phases but an appreciable degree of mosaicity in as-grown BRST single-crystals which remains unaffected by the annealing process. Energy-dispersive x-ray analysis showed that the annealed samples have a more homogeneous stoichiometric distribution of both Fe and Se with virtually the same content of interstitial Fe as the non-annealed ones. Thus, we conclude that the excess of Fe, in contrast to structural disorder, contributes to decrease the superconducting upper-critical fields of this series. Finally, a scaling analysis of the fluctuation conductivity in the superconducting critical regime, suggests that the superconducting fluctuations have a two-dimensional character in this system.

Four new intermetallic phases R 3-δ FeAl 4-x Mg x Si 2 (R = Yb, Dy) and R 3-δ FeAl 4-x Mg x Ge 2 (R = Er, Y) were synthesized in Mg/Al (1:1 mol ratio) molten flux. These phases have a new structure type in tetragonal space group P4/mbm (a = 13.3479(9) Å, c = 4.0996(3) Å, Z = 4, and R1 = 0.0176 for Yb 2.77 FeAl 3.72 Mg 0.28 Si 2 ). The structure features iron in trigonal prismatic coordination by aluminum atoms. The prisms share trigonal faces to form chains running along the c-axis, similar to the chains seen in several related structures, including that of the previously reported competing phases R 5 Mg 5 Fe 4 Al 12 Si 6 (R = Gd, Dy, and Y). Occupancies of Mg, Al, and Si sites in Yb 2.77 FeAl 3.72 Mg 0.28 Si 2 were determined by single crystal X-ray and neutron diffraction, bond length analysis, and comparison to atom positions and bond lengths in the isostructural germanides. Electronic structure calculations indicate these phases are polar intermetallics with pseudogaps near the Fermi level. The magnetic properties of these phases are determined by the rare earth ions. Y 3-δ FeAl 4-x Mg x Ge 2 is Pauli paramagnetic; the Yb 3+ cations in Yb 2.77 FeAl 3.72 Mg 0.28 Si 2 exhibit Curie−Weiss behavior with no ordering in the temperature range observed. Er 3-δ FeAl 4-x Mg x Ge 2 and Dy 3-δ FeAl 4-x Mg x Si 2 order antiferromagnetically at T N = 2.8 and 4.0 K, respectively; the former undergoes a spin reorientation at ∼4400 G according to the ac field dependence of magnetization.