Neutron scattering study of the incommensurate magnetic order of UNi2Al3 in high magnetic fields

Elastic neutron scattering studies from a single crystal sample of the heavy fermion superconductor, UNi2Al3, have revealed the onset of long range magnetic order below TN = 4.6 K. This order is characterized by an incommensurate (IC) ordering wavevector given by (12 ± τ, 0, 12) with τ = 0.110 ± 0.003. Measurements performed in the presence of a magnetic field (up to 8 T) perpendicular to the (H, 0, L) plane show no variation in TN but have an effect on the intensity as well as on the IC wavevector component of the ordering wavevector. Our results are discussed in terms of the possible basal-plane orientations for the magnetic moment in this compound.