Indides LnNiIn2 (Ln=Pr, Nd, Sm) and Ferromagnetic PrRhIn

Abstract

The title compounds were synthesized by reacting the elements in an arc-melting 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, wR2=0.0550, 1451 F2 values, and 66 parameters. From a geometrical point of view, the structure of PrNiIn2 may be described as an intergrowth of small distorted CaCu5-, CsCl-, and Cu3Au-related slabs. The structure 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 channels. To a first approximation the formula may be written as Pr3+[NiIn2]3−. PrRhIn adopts the ZrNiAl type structure: P62m, a=755.6(2) pm, c=404.8(1) pm, wR2=0.0285, 361 F2 values, and 14 parameters. Structural motifs of PrRhIn are tricapped trigonal prisms [Rh1In6Pr3] and [Rh2Pr6In3]. The rhodium and indium atoms form a three-dimensional [RhIn] polyanion in which the praseodymium atoms are located in distorted hexagonal channels. Susceptibility measurements reveal Curie–Weiss behavior with a magnetic moment of 3.69(5) μB/Pr. PrRhIn orders ferromagnetically at TC=5.8(6) K and shows a saturation magnetization of 1.60(5) μB/Pr at 2 K and 5.5 T. Resistivity measurements indicate metallic behavior with a specific resistivity of 105±20 μΩ cm at room temperature.