METAL-INSULATOR-TRANSITION IN THE MIXED-VALENCE MANGANITES

It is found that the sharp resistivity peak observed near the Curie te mperature T-C in the manganites R(1-x)A(x)MnO(3) is closely correlated to the residual resistivity rho(0) of the sample, suggesting that non magnetic randomness plays an important role in determining their anoma lous properties. Using the one-parameter scaling theory to study the e lectronic localization due to both the nonmagnetic randomness and the double ex change spin disorder, we show that the sharp resistivity pea k is caused by the Anderson metal-insulator (M-I) transition and that rho(0)>rho(c) (a critical value) is a prerequisite to the occurrence o f the M-I transition. T-C as a function of rho(0) has also been calcul ated. These results are in good agreement with experimental measuremen ts.