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Investigation of non-magnetic iron in Lu/sub 2/Fe/sub 3/Si/sub 5/-type superconductors

Thesis/Dissertation ·
OSTI ID:6977195
A focused study on the effect of transition-metal substitution for Fe in the compounds Lu/sub 2/(Fe/sub 1-x/T/sub x/)/sub 3/Si/sub 5/ (where T = Cr, Mn, Co, Ni Cu, and Ru) is reported. The effect of these transition metals on the superconducting transition temperature shows that Cr, Co, Ni, and Ru all act as non-magnetic impurities. By fitting the experimental data T/sub c//T/sub co/ to Kaiser's equation, a good agreement with Kaiser's theory is obtained. The rate of suppression due to Co substitution is similar to that of Ru. Superconductivity persists (T/sub c/ = 0.49 K) even when 10 at. % Co is substituted for Fe. In contrast, Mn and Cu act as magnetic impurities and suppress T/sub c/ in a way described by the theory of Abrikosov and Gor'kov. The molar magnetic susceptibility of Lu/sub 2/Fe/sub 3/Si/sub 5/ does not follow a Curie-Weiss law, but rather increases slightly as temperature increases. The addition of Ru lowers the value of /sub X/(T), but the overall shape of /sub X/(T) is unchanged. In contrast, the substitution of the nominally magnetic transition metals Cr, Mn, Co and Ni for Fe causes /sub X/(T) to become more Curie-Weiss like. The magnetic susceptibility of the compound Lu/sub 2/CO/sub 3/Si/sub 5/ follows the Curie-Weiss law, while that of the compound Lu/sub 2/Ru/sub 3/Si/sub 5/ is diamagnetic. The electrical resistivity p(T) of the compound Lu/sub 2/Fe/sub 3/Si/sub 5/ is approximately quadratic in T at temperatures below 50 K and proportional to InT at temperature above 100 K.
Research Organization:
Iowa State Univ. of Science and Technology, Ames (USA)
OSTI ID:
6977195
Country of Publication:
United States
Language:
English