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Manganites Manganites provide a laboratory in which to study the interplay of a variety of magnetic, electronic and structural phases of matter in a strongly correlated electronic system. As in many strongly correlated electronic systems, the basic paradigm for manganite physics is the competition between the delocalising effects of the electron kinetic energy and the localizing effects of the Coulomb repulsion, aided by coupling to lattice degrees of freedom. When the kinetic energy is dominant, one finds a metallic ground state with ferromagnetic alignment of the core moments. When the localizing effects preponderate, instead we see charge and/or orbitally ordered ground states with substantial local lattice distortions from the near cubic symmetry of the metal, along with insulating behaviour and antiferromagnetism. One may tune between these two phases by many external parameters, especially chemical substitution, but also lattice strain, and magnetic field. The competition between metal and insulator is famously evident in the phenomenon of bulk colossal magnetoresistance, where a magnetic field tunes the conductivity of the material, and even more clearly in the strong tendency toward phase separation and inhomogeneity and regimes of percolative transport.

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