Several rare earth metal containing pseudo-ternary compounds in the RE2TAl3 series (RE=Sc, Y, La–Nd, Sm, Gd–Lu; T=Ru, Rh, Ir) have been synthesized from the elements by arc-melting or in tantalum capsules. Within the Rh series, the compounds with RE=La–Nd crystallize in the cubic MgCu2-type (Fd3̅m) structure. For Sm besides the cubic Laves phase also the hexagonal Laves phase (MgZn2 type, P63/mmc) is found. For the remaining compounds of both series, also the hexagonal MgZn2-type structure is observed. The structures of Ho2Ru0.96(1)Al3.04(1) (a=547.4(1), c=875.7(1) pm, wR=0.0397, 201 F2 values, 13 variables), Sc2Rh1.01(1)Al2.99(1) (a=528.0(1), c=852.8(1) pm, wR=0.0228, 184 F2 values, 13 variables), Ho2Rh1.00(1)Al3.00(1) (a=546.5(1), c=873.8(1) pm, wR=0.0590, 222 F2 values, 13 variables) and Tb2Ir1.06(1)Al2.94(1) (a=550.8(1), c=870.0(1) pm, wR=0.0743, 221 F2 values, 13 variables) have been refined from single-crystal data, indicating T/Al mixing on both crystallographic Zn sites of the aristotype. The Sc, Y, La and Lu containing compounds exhibit Pauli-paramagnetic behavior, while the other compounds show paramagnetism, in line with the rare earth atoms in the trivalent oxidation state. Ferro- and antiferromagnetic ordering up to TC=50.2(1) K for Gd2RhAl3 is observed, while Sm2RuAl3 shows van Vleck paramagnetism and Yb2RuAl3, finally, exhibits only partially trivalent Yb atoms, evident from a reduced magnetic moment and increased lattice parameters.
The germanides RE3Pt4Ge6 (RE=Y, Pr, Nd, Sm, Gd–Dy) have been synthesized by arc-melting of the elements followed by inductive annealing to improve the crystallinity and allow for structural order. The compounds have been studied by powder X-ray diffraction; additionally the structure of Y3Pt4Ge6 has been refined from single-crystal X-ray diffractometer data. It exhibits a (3+1)D modulated structure, indicating isotypism with Ce3Pt4Ge6. The crystal structure can be described as an intergrowth between YIrGe2- and CaBe2Ge2-type slabs along [100]. Temperature-dependent magnetic susceptibility measurements showed Pauli paramagnetism for Y3Pt4Ge6 and Curie-Weiss paramagnetism for Pr3Pt4Ge6 and Nd3Pt4Ge6. Sm3Pt4Ge6 exhibits van Vleck paramagnetism, while antiferromagnetic ordering at TN=8.1(1) K and TN=11.0(1) K is observed for Gd3Pt4Ge6 and Tb3Pt4Ge6, respectively.
Over 20 new compounds of the RE6T5Al7 series (RE = Sc, Y, Ce–Nd, Sm, Gd–Lu; T = Ru, Ir; Yb6Ir5Ga7 type structure; superstructure of MgZn2; fully ordered Nb6.4Ir4Al7.6 type) have been synthesized. They crystallize in the hexagonal crystal system with space group P63/mcm. Their lattice parameters are in the ranges of a = 935–963 and c = 851–874 pm for the RE6Ru5Al7 and a = 913–966 and c = 825–865 pm for the RE6Ir5Al7 series. Four structures (Ho6Ru5Al7, Yb6Ru4.68(1)Al7.32(1), Sc6Ir5Al7, and Ho6Ir4.53(1)Al7.47(1)) have been refined from single-crystal data, indicating fully ordered structures for Ho6Ru5Al7 and Sc6Ir5Al7; however, T/Al mixing was observed on one crystallographic site for Ho6Ir4.53(1)Al7.47(1) and on two sites for Yb6Ru4.68(1)Al7.32(1). The Sc-, Y-, and Lu-containing compounds exhibit Pauli paramagnetism in line with a filled d band for Ru and Ir. Ce6Ru5Al7 exhibits mixed-valent behavior, while Yb6Ru5Al7 is solely trivalent. The other compounds exhibit paramagnetism and ferromagnetic phase transitions up to temperatures of T C = 83.4(1) K for Gd6Ru5Al7. In addition to the basic magnetic characterizations and studies of the electrical resistivity and heat capacity, the magnetocaloric properties of Gd6Ru5Al7, Tb6Ru5Al7, and Dy6Ru5Al7 have been investigated, revealing magnetic entropy changes of −ΔS M max = 6.2(1), 7.7(1), and 5.4(1) J kg–1 K–1 (0 → 5 T) and relative cooling powers RCP = 242, 207, and 135 J kg–1, respectively. For a deeper insight into the second-order magnetic phase transitions, the critical behavior was investigated according to the scaling hypothesis. The critical behavior of Gd6Ru5Al7 is in accordance with the mean-field theory; the critical exponents of Tb6Ru5Al7 and Dy6Ru5Al7, however, deviate strongly from this universality class. For comparison of the structural and magnetic properties, the thus far unstudied members of the RERuAl series (RE = Sc, Y, Sm, Gd–Lu; MgZn2 type) have additionally been prepared and characterized.
Abstract. The compounds of the REPt 6 Al 3 series (RE = Ce-Nd, Sm, Gd, Tb) were obtained by reaction of the elements via arc-melting. They were characterized by powder and single-crystal X-ray diffraction (NdPt 6 Al 3 : wR = 0.0432, 759 F 2 values, 33 variables) as well as by magnetic susceptibility measurements. The isostructural compounds crystallize with a new structure type in the trigonal crystal system with space group R3c, twelve formula units in the unit cell, and lattice parameters of a = 752-755 and c = 3882-3945 pm. The crystal structure can be described by different slabs stacked along [001]. One layer
The intermetallic phase ErPd
The ternary rare‐earth iridium gallides RE6Ir5Ga7 (RE = Sc, Y, Nd, Sm, Gd – Tm, and Lu) were synthesized from the elements by arc‐melting or by induction melting in sealed niobium ampoules. The samples were structurally characterized by X‐ray powder diffraction. The structure of Sc6Ir5Ga7 was refined from single‐crystal X‐ray diffractometer data: Yb6Ir5Ga7 (Nb6.4Ir4Al7.6) type, P63/mcm, a = 912.84(7), c = 828.07(6) pm, wR2 = 0.0362, 504 F2 values and 22 variables. The RE6Ir5Ga7 gallides crystallize with a fully ordered superstructure of the hexagonal Laves phase MgZn2. The zinc substructure consists of ordered and condensed Ir3Ga and IrGa3 tetrahedra. Further phase analytical studies in the RE‐Ir‐Ga systems led to the new equiatomic gallides SmIrGa and LuIrGa with the orthorhombic, TiNiSi type structure, space group Pnma. The samarium compound shows a pronounced solid solution SmIr1–xGa1+x, which was confirmed by single crystal structure refinements for SmIr0.95Ga1.05, SmIr0.69Ga1.31 and SmIr0.55Ga1.45. The RE6Ir5Ga7 and REIrGa gallides show pronounced covalent Ir–Ga bonding.
Abstract:The REPt 2 Al 3 compounds of the late rare-earth metals (RE = Y, Dy-Tm) were found to crystallize isostructural. Single-crystal X-ray investigations of YPt 2 Al 3 revealed an orthorhombic unit cell (a = 1080.73(6), b = 1871.96(9), c = 413.04(2) pm, wR2 = 0.0780, 942 F 2 values, 46 variables) with space group Cmmm (oC48; q 2 pji 2 hedb). A comparison with the Pearson database indicated that YPt 2 Al 3 forms a new structure type, in which the Pt and Al atoms form a [Pt 2 Al 3 ] δ− polyanion and the Y atoms reside in the cavities within the framework. Via a group-subgroup scheme, the relationship between the PrNi 2 Al 3 -type structure and the new YPt 2 Al 3 -type structure was illustrated. The compounds with RE = Dy-Tm were characterized by powder X-ray diffraction experiments. While YPt 2 Al 3 is a Pauli-paramagnet, the other REPt 2 Al 3 (RE = Dy-Tm) compounds exhibit paramagnetic behavior, which is in line with the rare-earth atoms being in the trivalent oxidation state. DyPt 2 Al 3 and TmPt 2 Al 3 exhibit ferromagnetic ordering at T C = 10.8(1) and 4.7(1) K and HoPt 2 Al 3 antiferromagnetic ordering at T N = 5.5(1) K, respectively. Attempts to synthesize the isostructural lutetium compound resulted in the formation of Lu 2 Pt 3 Al 4 (Ce 2 Ir 3 Sb 4 -type, Pnma, a = 1343.4(2), b = 416.41(8), c = 1141.1(2) pm), which could also be realized with thulium. The structure was refined from single-crystal data (wR2 = 0.0940, 1605 F 2 values, 56 variables). Again, a polyanion with bonding Pt-Al interactions was found, and the two distinct Lu atoms were residing in the cavities of the [Pt 3 Al 4 ] δ-framework. X-ray photoelectron spectroscopy (XPS) measurements were conducted to examine the electron transfer from the rare-earth atoms onto the polyanionic framework.
The intermetallic solid solution CePd1−xAuxAl (x = 0.1–0.9) has been synthesized from the elements by arc-melting and subsequent annealing in induction followed by tube furnaces. The samples were characterized using the Guinier powder diffraction technique and the structures of the nominal compositions CeAuAl and CePd0.2Au0.8Al were refined from single crystal X-ray diffractometer data. For small values of x = 0.1–0.3, the compounds crystallize in the hexagonal ZrNiAl-type structure (space group P$‾{6}$2m), while for x = 0.5–0.9 the orthorhombic TiNiSi-type structure (space group Pnma) was observed. In both structure types, the transition metal and aluminum atoms form a complex polyanionic network with the cerium atoms filling the respective cavities. The transition metal atoms are in both cases surrounded in the shape of a tri-capped trigonal prism, the connectivity of these units, however, is different. Temperature-dependent magnetic susceptibility measurements of all compounds indicated a stable trivalent oxidation state for the cerium atoms along with antiferromagnetic ordering around TN ∼ 3 K.
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