Neutron scattering study on U-dichalcogenides

Metoki, Naoto   ; Kaneko, Koji   ; Ikeda, Shugo*; Sakai, Hironori   ; Yamamoto, Etsuji  ; Haga, Yoshinori   ; Homma, Yoshiya*; Shiokawa, Yoshinobu*

Inelastic neutron scattering study has been carried out on US. A clear crystalline electric field (CEF) peak has been observed at 7.4 meV, which is consistent with the level scheme obtained from susceptibility data assuming 5f configuration. The CEF becomes very weak and broad, and a quasi-elastic response emerges above the characteristic temperature 100 K. It indicates the crossover of the 5f character between localized and itinerant. A quasi-elastic response can be concluded as the hybridization effect of the 5f electrons with ligand p-electrons. Our study suggests that the crossover of the 5f character is the origin of the metal-insulator transition in US.