Nature of electrical hopping conduction and magnetotransport studies in the electron doped manganite Ca0.85Gd0.15MnO3

• Temperature and magnetic field dependent resistivity of Ca0.85Gd0.15MnO3 was studied.
• Small polaron hopping (SPH) dominates above charge ordering temperature (TCOTCO).
• Resistivity follows parallel combination of SPH and VRH model below TCOTCO.
• Conductivity exhibited a variable range hopping (VRH) model at low temperature.
• Magnetoresistance is governed by spin-polarized tunneling at grain boundaries.

The magnetotransport properties of Ca0.85Gd0.15MnO3 have been studied analyzing the temperature and magnetic field dependent resistivity. High temperature (T>TCOT>TCO: charge ordering temperature) conductivity has been found to be described by the non-adiabatic small polaron hopping (SPH) model. The manganite shows a parallel combination of SPH and variable range hopping (VRH) model below TCOTCO. VRH model fits the corresponding low temperature data. The field depended magnetoresistance (MR) has been investigated with a phenomenological model considering the spin-polarized tunneling. The field dependent MR in scaled coordinate collapses into single curve demonstrating the temperature-independent behavior.