Crystal structure refinements and magnetic behavior of U₆Ni, UNi₅, UNi₂ and the substitution derivative UNi_1.7Si_0.3

Chem. Met. Alloys 1 (2008) 54-57

https://doi.org/10.30970/cma1.0034

A. PERRICONE, H. NOËL

The crystal structures of the binaries U₆Ni, UNi₂ and UNi₅ have been refined for the first time from single crystal data. U₆Ni crystallizes in the tetragonal system, U₆Mn type, s.g. I4/mcm, with lattice parameters a = 10.3835(8) Å, c = 5.1565(4) Å. The uranium atoms occupy 8h (U1) and 16k (U2) Wyckoff positions, and the Ni atoms a 4a position. UNi₅ crystallizes in the cubic AuBe₅ type, s.g. F-43m, with a = 6.7958(6) Å and the following atom site occupations: U in 4a, Ni1 in 16e and Ni2 in 4c. UNi₂ crystallizes in the hexagonal MgZn₂ type, s.g. P6₃/mmc, with a = 4.9701(4) Å, c = 8.2527(8) Å. Uranium occupies a 4f position and the nickel atoms are in 2a (Ni1) and 6h (Ni2) positions. The shortest interatomic U-U distances are 2.619(2) Å in U₆Ni, 3.026(1) Å in UNi₂, and 4.805(1) Å in UNi₅. UNi₂ shows itinerant ferromagnetism below 25 K, which vanishes with substitution of silicon for nickel.

Thermal variation of the magnetization and of the reverse susceptibility under 5 kGauss for UNi₂.

Keywords

Uranium compounds / Intermetallics / Crystal structure / Magnetic properties