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Report No.

Comparative study of structures and electrical properties in cobalt-fullerene mixtures by systematic change of cobalt content

Sakai, Seiji; Naramoto, Hiroshi*; Avramov, P.; Yaita, Tsuyoshi; Lavrentiev, V.; Narumi, Kazumasa; Baba, Yuji  ; Maeda, Yoshihito

A systematic study is performed for the Co content-dependent structure evolution and electrical properties in the cobalt(Co)-fullerene(C$$_{60}$$) mixtures in the broad content region. Raman analysis confirms that the mixture has a saturation composition of Co$$_{5}$$C$$_{60}$$ for the compoundformation. An important role of the covalent Co-C bonds for the characteristic structure and the properties in the Co-C$$_{60}$$ compounds is concluded from the content-dependent peak shifts and the symmetry lowering of C$$_{60}$$. The Co-dilute mixtures exhibit a semiconductive nature represented bythe activated transport from the shallow mid-gap states. The Co-dense mixtures are characterized by hopping conduction (including variable rangehopping) attributed to the Co clusters/nanoparticles in the compound matrix and by the percolated metallic conduction, depending on the Co content.



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Category:Materials Science, Multidisciplinary



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