Magnetic separation and inelastic tunneling in self-doped manganite films

Magnetic and transport properties of 100 nm thick La0.9MnO3-delta self-doped manganite films have been investigated in the temperature range 5-300 K. The films exhibit a paramagnetic to ferromagnetic transition at T-C = 194 K. The temperature dependence of the resistivity shows a metal-insulator transition at 204 K and a strong resistivity increase below 160 K. The magnetoresistance was always negative and slightly bias dependent. Variations in resistivity with magnetic field and current are nonhysteretic, while the temperature dependence of the resistivity exhibits unusual inverse thermal hysteresis. The magnetic field independent inverse thermal hysteresis is strongly influenced by a thermal history of the sample. The data suggest that nonlinear low temperature transport is dominated by inelastic tunneling through intrinsic tunnel junctions formed by phase-separated ferromagnetic metallic domains and insulating anti ferromagnetic matrix. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3197855]