Variable range hopping conductivity in manganites

The nature of variable range hopping (VRH) conductivity which is observed in the insulating state of doped rare-earth manganites with perovskite structure is considered in the two component model of metallic-like droplets embedded in dielectric matrix. When the density of the metallic droplets is less than the percolation limit, the system falls into the insulating state with VRH conductivity defined by inter granular tunneling and electrostatic barriers. With temperature increasing the VRH regime is transforming into the hopping regime of small radius polarons. (C) 2012 Elsevier Ltd. All rights reserved.