Lattice and magnetic effects in doped manganites

The 'double exchange' mechanism and Jahn—Teller instabilities are shown to account for the low-temperature properties of slightly doped LaMnO₃ in the framework of the band insulator model. Analysis of the doping of La_1-xA_xMnO₃ with divalent A atoms suggests that Coulomb forces cause holes to be localized near dopants, which makes the formation of conducting clusters along these charged centers a major factor in the physics of such compounds. A percolation theory analysis of experimental data is given. The two-phase coexistence regime and the large-volume Fermi surface at high concentrations are discussed. The relevance of some of the results to doping physics in cuprates is suggested.