NMR study of plutonium dioxide PuO

Tokunaga, Yo  ; Haga, Yoshinori   ; Sakai, Hironori   ; Kambe, Shinsaku  ; Homma, Yoshiya*; Aoki, Dai*; Fujimoto, Tatsuya; Ikeda, Shugo; Matsuda, Tatsuma; Yamamoto, Etsuji  ; Nakamura, Akio; Shiokawa, Yoshinobu*; Nakajima, Kunihisa  ; Arai, Yasuo; Onuki, Yoshichika*

O NMR measurements have been performed on a series of the actinide dioxides, UO, NpO and PuO. Although the O NMR spectra in these materials are similar at higher temperatures, the low-temperature spectra present are significantly different. In UO we have observed a wide spectrum, forming a rectangular shape below =30 K. In NpO, on the other hand, the spectra broaden rather gradually and exhibit a two-peak structure below K. In PuO, neither spectrum broadening nor splitting has been observed. We show that these NMR spectra clearly indicate the different nature of the low-temperature magnetic ground states in these actinide compounds.