Electron-Lattice Coupling in Manganites and Cuprates

The lattice effects of charge localization in manganites and cuprates arediscussed from the local structural point of view. Pulsed neutron atomicpair-density function (PDF) analysis indicates that in La1−xSrxMnO3the realstructure deviates from the average crystal structure, and the localJahn–Teller (JT) distortion of Mn3+O6octahedra remains even in themetallic phase. This leads to a concept of the critical ionic size factorfor the formation of JT polarons. The colossal magnetoresistance (CMR)phenomena are observed in the crossover region from localized to delocalizedcharge states. This concept also explains the asymmetry of the phase diagramwhich is difficult to understand in the current band picture. Similarconsideration may help understand the lattice effects in superconductingcuprates.