Neutron scattering study of the static and dynamic magnetic properties of UNi2Al3

The static and dynamic magnetic properties of the heavy fermion superconductor UNi2Al3 have been studied using spherical neutron polarimetry (SNP) and three-axis spectroscopy (TAS), respectively. The SNP measurements give strong evidence that, in the incommensurate antiferromagnetic state and without applied external field, the magnetic moments lie in the basal plane with a dominant component along the a*-direction. The form of the structure is a longitudinally modulated spin-density wave. The TAS experiments reveal quasi-elastic magnetic scattering in the vicinity of the ordering wave vector. These results are compared to those determined for the isostructural compound UPd2Al3