Syntheses, crystal structures, and properties of EuRhIn, EuIr2, and EuIrSn2

The title compounds mere prepared from the elements by reactions in sealed tantalum tubes in a high-frequency furnace. Their structures were refined f rom single crystal X-ray diffractometer data: Pnma, a = 744.4(1) pm, b = 43 4.15(9) pm, c = 845.5(1) pm, wR2 = 0.0433, 658 F-2 values, 20 variables for EuRhIn, Fd3m, a = 756.5(1) pm, wR2 = 0.0349, 94 F-2 values, 5 variables fo r EuIr2, and Cmcm, a = 434.78(3) pm, b = 1124.0(1) pm, c = 751.20(5) pm, wR 2 = 0.0561, 565 F-2 values, 16 variables for EuIrSn2. EuRhIn crystallizes w ith a TiNiSi type structure that consists of strongly puckered Rh,In, hexag ons. The europium atoms fill the channels within the three-dimensional [RhI n] polyanion. EuRhIn orders ferromagnetically at 22.0(5) K with a saturatio n magnetic moment of 6.7(1) mu(B)/Eu at 4 K and 5.5 T. The divalent charact er of the europium atoms in EuRhIn was determined from temperature dependen t susceptibility (7.9 mu(B)/Eu in the high-temperature part) and Eu-151 Mos sbauer spectroscopic experiments. The latter show an isomer shift of delta = -8.30(2) mm/s at 78 It. At 4.2 K full magnetic hyperfine field splitting subjected to significant quadrupole splitting of Delta E-Q = 8 mm/s is obse rved. EuRhIn is a metallic conductor with a room temperature value of 58 mu Omega cm for the specific resistivity. The structure of the Laves phase Eu Ir2 is confirmed on the basis of single crystal X-ray data. The iridium ato ms form a tetrahedral network with Ir-Ir distances of 268 pm. EuIrSn2 adopt s a MgCuAl2 type structure that may be described as an iridium-filled varia nt of a distorted CaIn2-like sublattice of composition EuSn2. The tin atoms in the distorted and puckered hexagonal network have shorter (303 and 322 pm) and longer (343 pm) tin-tin contacts. (C) 1999 Academic Press.