Substitutional disorder and charge localization in manganites

In the manganites $R{E}_{1-x}A{E}_x$MnO${}_3$ ($RE$ and $AE$ being rare-earth and alkaline-earth elements, respectively) the random distribution of $R{E}^{3+}$ and $A{E}^{2+}$ induces random, but correlated, shifts of site energies of charge carriers in the Mn sites. We consider a realistic model of this diagonal disorder, in addition to the double-exchange hopping disorder, and investigate the metal-insulator transition as a function of temperature, across the paramagnetic-ferromagnetic line, and as a function of doping $x$. Contrary to previous results, we find that values of parameters, estimated from the electronic structure of the manganites, are not incompatible with the possibility of a disorder induced metal to insulator transition accompanying the ferromagnetic to paramagnetic transition at intermediate doping ($x\sim 0.2-0.4$). These findings indicate clearly that substitutional disorder has to be considered as an important effect when addressing the colossal magnetoresistance properties of manganites.