Temperature dependence of magnetoresistance and nonlinear conductance of the bicrystal grain boundary in epitaxial $La0.67Ba0.33MnO3$ thin films Available to Purchase

We investigated conduction through an artificial grain-boundary junction made in $La0.67Ba0.33MnO3$ thin films, deposited on a 36.7° $SrTiO3$ bicrystal substrate using a laser ablation technique. The grain boundary exhibits substantial magnetoresistance at low temperatures and also shows nonlinear $I–V$ characteristics. Analysis of temperature dependence of the dynamic conductance allows us to identify three carrier transport mechanisms across the grain boundary. These mechanisms exist in parallel, and at a given temperature one mechanism may dominate. Particularly, at higher temperatures $(T>175 K)$ the transport across the grain boundary involves spin–flip scattering, which we establish leads to decrease of the bicrystal grain-boundary contribution in magnetoresistance. At lower temperature (4.2–45 K), tunneling through a disordered oxide at the grain boundary dominates, whereas in the temperature range from 100 to 175 K, carrier transport is dominated by inelastic tunneling via pairs of manganese atoms.