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

5遍歴反強磁性体UNiGa及びUPtGaの結晶構造と磁気構造の中性子散乱実験

常盤 欣文; 芳賀 芳範   ; 目時 直人   ; 石井 慶信; 大貫 惇睦

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

UNiGaとUPtGaの中性子散乱実験を行い、これらの物質の磁気構造を決定した。UNiGaはNelタイプの磁気構造を持ち、磁気モーメントは[001]方向を向いており、の大きさは0.9,/Uであった。一方、UPtGaでは、反強磁性伝播ベクトルが[001/2]で磁気モーメントは[001]方向を向いている。そして磁気モーメントの大きさは0.24,/Uと見積もられた。UNiGaとUPtGaにおける磁気構造の違いの起源は今のところ明らかではない。

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.