Quasiparticle state in 4 localized ferromagnet CeRuGe studied by soft X-ray photoemission spectroscopy

Kawasaki, Ikuto  ; Fujimori, Shinichi   ; Takeda, Yukiharu   ; Yamagami, Hiroshi; Onuki, Yoshichika*

The electronic state of 4 localized ferromagnet CeRuGe has been investigated by angle-resolved photoemission spectroscopy (APRES) experiments using soft X rays. The band structure and Fermi surfaces consisting of non-4 bands are almost consistent with a calculation based on the density-functional theory for LaRuGe, thus confirming a localized character of the 4 electrons. On the other hand, the Ce 3-4 resonant ARPES experiments demonstrated that the 4 spectral function is dominated by components in the vicinity of the Fermi level and thus is different from that expected for a localized electron system. We also revealed that the intensities of the components have almost no temperature dependence up to at least 100 K, which is two orders of magnitude larger than the Kondo temperature of CeRuGe.