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 La_1-xSrₓMnO₃, we study systems with decreased content of Mn ions, such as single crystals of LaGa_1-xMnₓO₃ $(0<x<0.5).$ 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 LaGa_1-xMnₓO₃ 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.