Single-crystal growth and magnetic properties of a new ternary uranium compound UNiAl

Haga, Yoshinori   ; Matsuda, Tatsuma; Ikeda, Shugo; Galatanu, A.; Matsumoto, Takuya*; Sugimoto, Toyonari*; Tada, Toshiji*; Noguchi, Satoru*; Onuki, Yoshichika

A new ternary uranium-based intermetallic compound UNiAl has been symthesized. It crystallizes in the unique flat orthorhombic structure. Uranium atoms occupy two crystallographic 4 and 8 sites where local chemical environments are quite similar. The temperature dependence of the magnetic susceptibility demonstrates peculiar magnetic anisotropy; along - and -axes obeys the Curie-Weiss law above 23 K, while along -axis is small and temperature independent. At 23 K, only shows a sharp cusp corresponding to the antiferromagnetic ordering, while remains paramagnetic behavior down to 2 K. These results and crystallographical considerations lead to a conclusion that only uranium atoms at the 8 site order antiferromagnetically at = 23 K, while uranium atoms at the site do not order down to 50 mK.