Neutron Scattering Study of the Crystal and Magnetic Structures in Itinerant-5f Antiferromagnets UNiGa₅ and UPtGa₅

抄録

The crystal and magnetic structures of 5f itinerant antiferromagnets UNiGa₅ and UPtGa₅ were studied by means of neutron scattering. The powder diffraction data were well explained by the HoCoGa₅ tetragonal structure with space group P4/mmm. In UNiGa₅, uranium spins in the simple tetragonal lattice have a Néel-type structure with a relatively large moment of 0.9 μ_B/U along the [0,0,1] direction. On the other hand, magnetic moments of uranium atoms in UPtGa₅ are aligned ferromagnetically in the (0,0,1) plane and are directed along the [0,0,1] direction in an antiferromagnetic sequence (↑↓). An ordered moment is 0.24 μ_B/U. The nearest-neighbor interaction might be different in these isostructural compounds.