Element and orbital-specific observation of two-step magnetic transition in NpNiGa; X-ray magnetic circular dichroism study

Okane, Tetsuo  ; Okochi, Takuo*; Inami, Toshiya; Takeda, Yukiharu   ; Fujimori, Shinichi   ; Kawamura, Naomi*; Suzuki, Motohiro*; Tsutsui, Satoshi*; Yamagami, Hiroshi; Fujimori, Atsushi; Tanaka, Arata*; Aoki, Dai*; Homma, Yoshiya*; Shiokawa, Yoshinobu*; Yamamoto, Etsuji  ; Haga, Yoshinori   ; Nakamura, Akio; Onuki, Yoshichika*

X-ray magnetic circular dichroism (XMCD) experiments were performed at the Np and the Ga absorption edges of NpNiGa to investigate the temperature-dependent changes of magnetic properties of Np 5 and Ga 4 electron states. By the sum-rule analysis of the Np XMCD data, the orbital magnetic moment and the spin magnetic moment were estimated for the Np 5 and 5 electronic configurations, and their comparison with the previous magnetization and neutron scattering experiments suggests that the 5 configuration is more likely than the 5 configuration in NpNiGa. It was found that tends to increase from the high-temperature low-moment ordered state to the low-temperature high-moment ordered state.