Magneto-transport characteristics of electron-doped Ca0.85Sm0.15MnO3 manganite: Hopping and tunneling

• Temperature and magnetic field dependent resistivity of Ca0.85SM0.15MnO3 was studied.
• Small polaron hopping dominates at high-T region.
• ρ(T) exhibited a variable range hopping model at low-T region.
• Low-ρ state has been explained by the kinetic arrest of electronic phase.
• Magnetoresistance is governed by spin-polarized tunneling between the adjacent grains.

In this work we have reported the temperature and magnetic field dependence of resistivity and magnetoresistance in electron-doped polycrystalline Ca0.85Sm0.15MnO3 (CSMO). It shows a robust semiconducting behavior down to the lowest temperature (5 K) of investigation. High-T resistivity of the present sample follows small polaron hopping (SPH) conduction mechanism. The variable range hopping (VRH) model has been found to fit low-T resistivity data. Intermediate-temperature ρ(T) data has been explained using a parallel combination of SPH and 3D-VRH model. The resistivity shows strong dependence on the magnetic field–temperature history. Magnetoresistance (MR) of the sample shows strong irreversibility with respect to sweeping of the field between the highest positive and negative values. Low-ρ state of the envelope curve in MR indicates a manifestation of kinetic arrest of the electronic phase on application of magnetic field. We demonstrates that the sizable MR at low fields dominated by spin-polarized tunneling between the adjacent grains.