Indides LnNiIn(2) (Ln = Pr, Nd, Sm) and ferromagnetic PrRhIn

The title compounds were synthesized by reacting the elements in an are-mel ting apparatus under purified argon and subsequent annealing at 970 K, The nickel containing compounds crystallize with a new structure type which was determined for PrNiIn2,: Cmcm, a = 440.0(2) pm, b = 1833.9(6) pm, c = 2164 .6(5) pm, wR(2) = 0.0550, 1451 F-2 values, and 66 parameters. From a geomet rical point of view, the structure of PrNiIn2 may be described as an interg rowth of small distorted CaCu5-, CsCl-, and Cu3Au-related slabs. The struct ure is also related to the MgCuAl2 type by chemical twinning, The shortest interatomic distances within the PrNiIn2 structure occur for the Ni-In and In-In contacts. The nickel and indium atoms form a three-dimensional [NiIn2 ] polyanion in which the praseodymium atoms fill distorted pentagonal chann els. To a first approximation the formula may be written as Pr3+[NiIn2](3-) . PrRhIn adopts the ZrNiAl type structure: P (6) over bar 2m, a = 755.6(2) pm, c = 404.8(1) pm, wR(2) = 0.0285, 361 F-2 values, and 14 parameters. Str uctural motifs of PrRhIn are tricapped trigonal prisms [Rh1In(6)Pr(3)] and [Rh2Pr(6)In(3)]. The rhodium and indium atoms form a three-dimensional [RhI n] polyanion in which the praseodymium atoms are located in distorted hexag onal channels. Susceptibility measurements reveal Curie-Weiss behavior with a magnetic moment of 3.69(5) mu(B)/Pr. PrRhIn orders ferromagnetically at T-C = 5.8(6) K and shows a saturation magnetization of 1.60(5) mu(B)/Pr at 2 K and 5.5 T. Resistivity measurements indicate metallic behavior with a s pecific resistivity of 105 +/- 20 mu Omega cm at room temperature. (C) 2000 Academic Press.