Neutron scattering study of the crystal and magnetic structures in itinerant-5 antiferromagnets UNiGa and UPtGa

Tokiwa, Yoshifumi; Haga, Yoshinori   ; Metoki, Naoto   ; Ishii, Yoshinobu; Onuki, Yoshichika

The crystal and magnetic structures of 5 itinerant antiferromagnets UNiGa and UPtGa were studied by means of neutron scattering. The powder diffraction data were well explained by the HoCoGa tetragonal structure with space group P4/mmm. In UNiGa uranium spins in the simple tetragonal lattice has the Nel-type structure with a relatively large moment of 0.9,/U along the [0,0,1] direction. On the other hand, magnetic moments of uranium atoms in UPtGa 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,/U. The nearest-neighbor interaction might be different in these isostructural compounds.