Magnetization densities in UCoAl studied by polarized neutron diffraction - art. no. 064423

UCoAI crystallizes in the ZrNiAl-type hexagonal structure, exhibits a param agnetic ground state, but a metamagnetic transition to a ferromagnetic stat e with uranium magnetic moments parallel to the c axis occurs at low temper atures when a field of 1 T is applied in this direction. We present the res ults of a polarized neutron experiment on a UCoAl single crystal. Experimen tal data have been analyzed by a maximum entropy method and within an atomi c model. The main magnetic contribution originates from the uranium atoms. The ratio mu (L)/mu (s) between the orbital and spin moment is slightly red uced in comparison to the uranium free ion value and remains nearly unchang ed between 1 and 8 T. Induced magnetic moments of nearly same magnitude and similar field dependence are observed on the two cobalt sites. An addition al magnetization density is observed around the aluminum positions. The res ults are discussed in context of former studies on isostructural UTX compou nds.