Low-temperature magnetic structure of UNiGe.

Abstract

We report on the magnetic structure of single-crystalline UNiGe in its low-temperature commensurate antiferromagnetic phase. UNiGe crystallizes in the orthorhombic TiNiSi structure type with space group {ital Pnma} and undergoes two magnetic transitions at 51 and 42 K. Our data, taken at 20 K, rule out both of the previously reported magnetic structures for the low-temperature phase, though we find an ordering vector {ital q}=(0,1/2,1/2) in agreement with the previous powder study of Murasik {ital et} {ital al}. [J. Phys. Condens. Matter {bold 3}, 1841 (1991)]. We observe both domains of the single-{ital q} structure, and show that this is preferred over a 2-{ital q} structure. We extract a moment of 0.91{mu}{sub {ital B}} per U atom, and it is likely that the moment lies within the {ital b}-{ital c} plane in a collinear moment-density-wave configuration. However, out-of-plane moment components are allowed by symmetry and our best refinement gives noncollinear canting out of the plane by approximately 20{degree}. This structure belongs to one of the two possible irreducible representations, and we discuss its relationship to a more conventional Shubnikov-group analysis. {copyright} {ital 1996 The American Physical Society.}