THEORY OF COLOSSAL MAGNETORESISTANCE IN R(1-X)A(X)MNO(3)

A localization model comprising spin disorder and nonmagnetic randomne ss is presented to account for novel magnetotransport properties in Mn oxides R(1-x)A(x)MnO(3). Localization length of electrons as a functi on of magnetization is determined by means of the transfer matrix meth od. Including the Coulomb interaction between electrons, the variable- range hopping resistivity is calculated as a function of temperature a nd magnetic field. The resulting sharp resistivity peak near the Curie temperature and, in particular, the magnitude of the colossal negativ e magnetoresistance are in good agreement with experimental measuremen ts.