| Summary: | Colossal magnetoresistance ceramics with the nominal composition of (La1-xYbx)2/3Ca1/3MnO3 (x=0 to 0.12) were synthesised, and their electrical transport and magnetoresistance behaviours were investigated. Experimental results showed that the metal-insulator transition temperature TMI of the ceramic is largely dependent on Yb substitution. Electrical resistivity as a function of temperature in zero field, ρ(0, T) gradually increased with Yb content up to x=0.1 but drastically decreased at x=0.12. The metallic region of the ρ(0, T) curve (T<TMI) of all Yb substituted samples was fitted to the model for electron-electron and electron-magnon scatterings while the insulating region was fitted to a model of polaron hopping with lowest activation energy Ea observed at x=0.10. The largest MR effect of 47% was observed at 0.4 T external field for x=0.10. It is suggested that the increase in ρ(0, T) is related to enhanced Jahn-Teller effect while the MR response is due to magnetic changes as a result of the introduction of Yb3+ magnetic ions. © W. S. Maney & Son Ltd. 2009.
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