Inter-grain tunneling conductivity of Sr2FeMoO6: effects of doping and grain-boundary modification

Abstract The inter-grain conductivity ( σ GB ) of polycrystalline and granular Sr 2 FeMoO 6 (SFMO) increases linearly with temperature between liquid He to room temperature at least. This very unusual behavior motivated the new investigations reported here. It was found that σ GB ( T ) is linear also for granular samples of La-doped SFMO and for sintered SFMO with modified grain boundaries (GBs), but it is nonlinear for granular samples of Ag- and Na-doped SFMO. The fluctuation-induced tunneling (FIT) model was successfully applied in the interpretation of both types of behavior. Current–voltage measurements were carried out on a resistive sample with oxygenated GBs, using pulsed high currents. The interpretation of the effect of a high electric field on transport, in terms of the FIT model, is discussed.