Magnetic studies on CoU2O6 and NiU2O6 by magnetic susceptibility, specific heat and neutron diffraction measurements

Magnetic properties of ternary uranium oxides CoU2O6 and NiU2O6 have been reported. X-ray and neutron diffraction measurements show that both compounds crystallize in the hexagonal Na2SiF6 structure (space group: P321), in which both cobalt (nickel) and uranium ions are in the distorted octahedral crystal field by six oxygen ions. Measurements of the magnetic susceptibility and specific heat reveal that CoU2O6 and NiU2O6 order antiferromagnetically at 32.5 and 35.3 K, respectively. Neutron diffraction measurements at 10 K show that the magnetic structure for CoU2O6 is a multi-sinusoidal structure with a propagation vector (0, 0, 1/6).