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

Abstract

For better understanding of the charge-transport mechanisms in perovskite manganites, along with colossal magnetoresistance (CMR) materials, such as ${\mathrm{La}}_{1-x}{\mathrm{Sr}}_x{\mathrm{MnO}}_3,$ we study systems with decreased content of Mn ions, such as single crystals of ${\mathrm{LaGa}}_{1-x}{\mathrm{Mn}}_x{\mathrm{O}}_3$ $\mathrm{}(0<x<\mathrm{}0.5\mathrm{}).$ 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 ${\mathrm{LaGa}}_{1-x}{\mathrm{Mn}}_x{\mathrm{O}}_3$ 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.