Room-temperature electronic phase transitions in the continuous phase diagrams of perovskite manganites

Highly correlated electronic systems-such as transition-metal oxides that a re doped Mott insulators-are complex systems which exhibit puzzling phenome na, including high-temperature superconductivity and colossal magnetoresist ivity. Recent studies(1-3) suggest that in such systems collective electron ic phenomena are important, arising from long-range Coulomb interactions an d magnetic effects. The qualitative behaviour of these systems is strongly dependent on charge filling (the level of doping) and the lattice constant. Here we report a time-efficient and systematic experimental approach for s tudying the phase diagrams of condensed-matter systems. It involves the con tinuous mapping of the physical properties of epitaxial thin films of perov skite manganites (a class of doped Mott insulator) as their composition is varied. We discover evidence that suggests the presence of phase boundaries of electronic origin at room temperature.