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Report No.

Ferromagnetism and giant magnetoresistance in the rare-earth fullerides Eu$$_{6-x}$$Sr$$_x$$C$$_{60}$$

Ishii, Kenji; Fujiwara, Akihiko*; Suematsu, Hiroyoshi*; Kubozono, Yoshihiro*

We have studied crystal structure, magnetism and electric transport properties of a europium fulleride Eu$$_6$$C$$_{60}$$ and its Sr-substituted compounds, Eu$$_{6-x}$$Sr$$_x$$C$$_{60}$$. They have a $$bcc$$ structure, which is an isostructure of other $$M_6$$C$$_{60}$$ ($$M$$ represents an alkali atom or an alkaline earth atom). Magnetic measurements revealed that magnetic moment is ascribed to the divalent europium atom with $$S$$ = 7/2 spin, and a ferromagnetic transition was observed at $$T_C$$ = 10 - 14 K. In Eu$$_6$$C$$_{60}$$, we also confirm the ferromagnetic transition by heat capacity measurement. The striking feature in Eu$$_{6-x}$$Sr$$_x$$C$$_{60}$$ is very large negative magnetoresistance at low temperature; the resistivity ratio $$rho$$($$H$$ = 9 T)/$$rho$$($$H$$ = 0 T) reaches almost 10$$^{-3}$$ at 1 K in Eu$$_6$$C$$_{60}$$. Such large magnetoresistance is the manifestation of a strong $$pi$$-$$f$$ interaction between conduction carriers on C$$_{60}$$ and 4$$f$$ electrons of Eu.



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Category:Materials Science, Multidisciplinary



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