Adiabatic small polaron-hopping conduction in Ln 0.85Ca 0.15MnO 3 (Ln=Nd, Pr and Sm) perovskites

Abstract

Polycrystalline bulk ferromagnetic insulating (FMI) Ln 0.85Ca 0.15MnO 3 (Ln=Nd, Pr and Sm) samples are prepared by standard solid-state reaction route and characterized. Powder X-ray diffraction (XRD) data of the manganites show single-phase character. Existing theoretical models predict that the high temperature ( T> θ D/2, θ D being the Debye temperature) dc conductivity ( σ dc) of these samples is due to adiabatic small polaron-hopping conduction. Greaves’ and Mott's variable range hopping (VRH) conduction mechanisms are not suitable to explain the σ dc data at low temperature ( T< θ D/2).