Dynamical mean-field solution for a model of metal-insulator transitions in moderately doped manganites

We propose that a specific spatial configuration of lattice sites that ener getically favor 3+ or 4+ Mn ions in moderately doped manganites constitutes approximately a spatially random two-energy-level system. Such an effect r esults in a mechanism of metal-insulator transitions that appears to be dif ferent from both the Anderson transition and the Mott-Hubbard transition. C orrespondingly, a disordered Kondo lattice model is put forward, whose dyna mical mean-field solution agrees reasonably with experiments. [S0163-1829(9 8)03047-1].