Neutron diffraction study of magnetic structure of U3Bi4 and U3Sb4

Experiments using polarized and unpolarized neutrons have been performed an single crystals of U3Bi4 and U3Sb4. A magnetic structure with a [001], easy axis and two types of uranium site having different values of the moment was found for both compounds. The values of magnetic moment at these two sites are 2.11 and 1.81 mu(B) for bismuthide, and 2.14 and 1.66 mu(B) for antimonide. The appearance of such a structure is ascribed to a low local symmetry of the U-ion environment and hybridization-mediated two-ion interactions.