Metal-insulator transition and non-adiabatic small polaron hopping conduction in electron-doped Ca0.85Pr0.15MnO3 manganite

Abstract

We report the detailed analysis of magnetic-field-dependent electrical transport properties of Ca0.85Pr0.15MnO3 (CPMO) over a wide temperature range (5–300 K) in absence and presence of applied magnetic fields as high as 15 T. The resistivity undergoes a metal-insulator (M-I) transition. We report the effect of magnetic field on the transition temperature that decreases with the applied field. The M-I transition in this compound may be due to the spin-state transition from a high spin state to a low spin state of Mn3+ ions. Temperature-dependent resistivity fitting above TMI (M-I transition temperature) suggests that electrical-conductivity carriers are mainly scattered by the electron–phonon interaction. In the semiconducting region, the conduction mechanism follows nonadiabatic, small-polaron hopping (SPH) above θD/2 (θD is the Debye temperature) and Mott-type variable range hopping (VRH) below θD/2. It has also been found that the density of states (DOS) at the Fermi level increases, whereas the hopping energy Whop decreases with external magnetic field.