Magnetic neutron diffraction on uranium intermetallics

Several isostructural families of uranium intermetallic compounds UTX, U2T2 X, and UT2 X 2 (T and X are transition metal and p-electron elements, respectively) with orthorhombic, hexagonal, tetragonal and cubic symmetry have been inves- tigated using unpolarized magnetic neutron diffraction at Los Alamos, Argonne and Chalk River National Laboratories. The aim has been to understand the role of hybridization, in relation to magnetocrystalline anisotropy and moment re- duction, as compared to the moment of the free ion obtained by Hund's rule. Representation theory, as well as magnetic (Shubnikov) space group analysis, has been used extensively to generate all possible magnetic structures allowed by symmetry. The refinements were done using both standard crystallographic packages and specially-written FORTRAN codes. The magnetic structures ob- tained range from a simple collinear-commensurate configuration in UCu1.5Sn 2 to a noncollinear-incommensurate configuration with two domains in UNiGe. The result is that hybridization plays an important role in determining both magnetic anisotropy and moment reduction.