Hopping conduction in charge-ordered rare-earth manganates Ln1−xCaxMnO3 (Lnrare earth)

Electrical resistivity behavior of single crystals as well as polycrystalline pellets of rare earth manganates has been investigated below the charge-ordering temperatures to understand the mechanism of conduction. The resistivity of both the single- and polycrystalline samples of Gd0.5Ca0.5MnO3 and Nd0.5Ca0.5MnO3 obey the T −1/4 law, characteristic of variable range hopping. A similar dependence is found in the hole-doped Pr0.6Ca0.4MnO3 as well, but the data of the electron-doped Pr0.4Ca0.6MnO3 do not seem to obey any T −1/n law satisfactorily. AC conductivity measurements also reflect the unusual nature of the electron-doped composition.