Magnetic behavior near the boundary of 4 delocalization in ferromagnetic CeRuGe and paramagnetic CeRuSi observed by Ce XAS and XMCD

Ce 吸収端でのXAS並びにXMCD測定による強磁性体CeRuGeと常磁性体CeRuSiの4非局在化境界近傍での磁性的振る舞いの研究

岡根 哲夫  ; 竹田 幸治   ; 山上 浩志; 藤森 淳; 松本 裕司; 木村 憲彰*; 小松原 武美*; 青木 晴善*

Okane, Tetsuo; Takeda, Yukiharu; Yamagami, Hiroshi; Fujimori, Atsushi; Matsumoto, Yuji; Kimura, Noriaki*; Komatsubara, Takemi*; Aoki, Haruyoshi*

X-ray absorption (XAS) and its magnetic circular dichroism (XMCD) were measured at the Ce absorption edges of ferromagnetic CeRuGe and paramagnetic CeRuSi: both compounds are considered to be located near the boundary of delocalization of Ce 4 electrons. While the XAS line shape varies clearly reflecting the variation in the 4 delocalization, the line-shape variation in XMCD is hardly discernible under various conditions of temperature and magnetic field. The XAS line-shape variation can be explained as effects of the variations in the 4 occupation number and in the ratio of = 7/2 states in the ground states, both of which are closely related to the 4 delocalization. The 4 delocalization also causes a decrease in the ratio of the orbital magnetic moment to the spin magnetic moment. The magnetic-field dependence of XAS suggests that the Ce 4 electrons retain a delocalized character across the metamagnetic transition in CeRuSi.