Intermetallics of the types REPd3X2 and REPt3X2 (RE=La–Nd, Sm, Gd, Tb; X=In, Sn) with substructures featuring tin and In atoms in distorted square-planar coordination

The intermetallic compounds RET3X2 (RE = La–Nd, Sm, Gd, Tb; T = Pd, Pt; X = In, Sn) have been synthesized from the elements by arc-melting and subsequent annealing sequences in tube or induction furnaces. The samples were characterized through Guinier powder diffraction patterns, and several structures were refined from single crystal X-ray diffractometer data. These indium and tin intermetallics crystallize with the orthorhombic CePd3In2-type structure, space group Pnma. The palladium (platinum) and indium (tin) atoms in the RET3X2 structures build up complex three-dimensional [T3X2]δ− polyanionic networks in which the rare earth atoms fill cavities. The striking structural motifs concern the indium, respectively tin substructures, in which part of the indium and tin atoms have distorted square planar homoatomic coordination environments: In1In12In22 units in PrPd3In2 with interatomic distances 325 pm In1–In1 and 332 pm In1–In2 as well as Sn1Sn12Sn22 units in PrPt3Sn2 with the larger distances of 356 pm for Sn1–Sn1 and of 344 pm for Sn1–Sn2. Temperature dependent magnetic susceptibility measurements have indicated Pauli paramagnetism or diamagnetism for the lanthanum compounds, van-Vleck paramagnetism for SmPt3In2 and Curie-Weiss paramagnetism for the remaining compounds. Antiferromagnetic ordering was detected at TN = 4.0(1) K for CePt3In2 and at TN = 3.5(1) K for SmPt3In2. CePt3In2 shows a metamagnetic transition at an external magnetic field of 47(3) kOe.

Rare earth-copper-magnesium intermetallics: crystal structure of CeCuMg, magnetocaloric effect of GdCuMg and physical properties of the Laves phases RECu4Mg (RE=Sm, Gd, Tb, Tm)

The intermetallic magnesium compounds CeCuMg and GdCuMg as well as the ternary Laves phases RECu4Mg (RE=Sm, Gd–Tm) were synthesized from the elements by different annealing sequences in high-frequency and muffle furnaces using niobium ampoules as crucibles. All samples were characterized through the lattice parameters using X-ray powder diffraction (Guinier technique). Two structures were refined from single-crystal X-ray diffractometer data: a=764.75(6), c=414.25(4) pm, space group P6̅2m, wR2=0.0389, 338 F2 values, 15 parameters for CeCuMg (ZrNiAl type) and a=723.18(2) pm, space group F4̅3m, wR2=0.0818, 91 F2 values, eight parameters for Gd1.06(3)Cu4Mg0.94(3) (MgCu4Sn type). The Laves phase shows a small homogeneity range (Gd/Mg mixing). An investigation of the magnetocaloric effect (MCE) of ferromagnetic GdCuMg (ZrNiAl type; TC=82 K) revealed a magnetic entropy change of ΔSM=6.5 J kg−1 K−1 and a relative cooling power of RCP=260 J kg−1 for a field change from 0 to 70 kOe, classifying GdCuMg as a moderate magnetocaloric material for the T=80 K region. Of the Laves phases RECu4Mg, SmCu4Mg shows van-Vleck paramagnetism above a Néel temperature of 10.8(5) K, whereas GdCu4Mg and TbCu4Mg undergo antiferromagnetic phase transitions at about 48 and 30 K, respectively. TmCu4Mg shows Curie-Weiss behavior in the entire temperature range. The electrical resistivity of SmCu4Mg and the specific heat capacity of GdCu4Mg were measured for further characterization.

Structural and magnetic investigations of the pseudo-ternary RE2TAl3 series (RE=Sc, Y, La–Nd, Sm, Gd–Lu; T=Ru, Rh, Ir) – size dependent formation of two different structure types

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 stannides REIr2Sn4 (RE=La, Ce, Pr, Nd, Sm)

The stannides REIr2Sn4 (RE=La, Ce, Pr, Nd, Sm) were synthesized from the elements by arc melting or by induction melting in sealed niobium containers. They crystallize with the NdRh2Sn4 type structure, space group Pnma. The samples were characterized by powder X-ray diffraction (Guinier technique). Three structures were refined from single-crystal X-ray data: a=1844.5(2), b=450.33(4), c=716.90(6) pm, wR2=0.0323, 1172 F2 values, 44 variables for LaIr2Sn4, a=1840.08(2), b=448.24(4), c=719.6(1) pm, wR2=0.0215, 1265 F2 values, 45 variables for Ce1.13Ir2Sn3.87, and a=1880.7(1), b=446.2(1), c=733.0(1) pm, wR2=0.0845, 836 F2 values, 45 variables for Ce1.68Ir2Sn3.32. The structures consist of three-dimensional [Ir2Sn4] polyanionic networks in which the rare earth atoms fill pentagonal prismatic channels. The striking structural motif concerns the formation of solid solutions RE1+xIr2Sn4−x on the Sn4 sites, which have similar coordination as the RE sites. Temperature dependent magnetic susceptibility measurements revealed diamagnetic behavior for LaIr2Sn4. CeIr2Sn4, PrIr2Sn4 and NdIr2Sn4 show Curie-Weiss paramagnetism while SmIr2Sn4 exhibits typical van Vleck paramagnetism. Antiferromagnetic ground states were observed for CeIr2Sn4 (TN=3.3 K) and SmIr2Sn4 (TN=3.8 K). 119Sn Mössbauer spectra show a close superposition of four sub-spectra which can be distinguished through their isomer shift and the quadrupole splitting parameter.

Van Vleck paramagnetism in undoped and Lu-doped bulk ceria

In Lu-doped CeO2 ceramics, the temperature independent magnetic susceptibility, usually attributed to Van Vleck-type magnetization, decreases linearly with Lu content.

Magnetic properties of the germanides RE3Pt4Ge6 (RE=Y, Pr, Nd, Sm, Gd–Dy)

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.

Synthesis, Crystal Structure and Physical Properties of Ba4Ti12O27

Polycrystalline sample of the reduced barium titanate Ba4Ti12O27 was prepared by solid state reaction in Ar atmosphere. The magnetic susceptibility was nearly temperature independent in the range of 75-300 K, suggesting the Van Vleck Paramagnetism. The temperature dependence of the electric conductivity does not obey any Arrhenius type behavior.