Conductivity and switching phenomena in Mn-doped perovskite single crystals and manganite thin films

For better understanding of the charge-transport mechanisms in perovskite manganites, along with colossal magnetoresistance ~CMR! materials, such as La12xSrxMnO3, we study systems with decreased content of Mn ions, such as single crystals of LaGa12xMnxO3 (0,x,0.5). The conductivity of all the systems in study can be described adequately with a nonadiabatic approximation of the hopping model with the values of the activation energy and resistivity coefficient strongly dependent on the concentration of Mn ions. Nonlinear voltage-current characteristics demonstrated switching to the low-resistivity state at high current density in LaGa12xMnxO3 crystals as well as in CMR films of low crystallinity. We explain the obtained results based on the small-polaron-hopping model, taking into account the heating processes and percolation effects.