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Oxide heterojunctions composed of manganite films of different tolerance factors and SrTiO3 : Nb are fabricated and their rectifying properties are experimentally studied. The current-voltage characteristics of the junctions are found to be dominated by diffusion current at high temperatures and by tunnelling current at low temperatures. Further analyses on the rectifying behaviours of the junctions indicate the occurrence of a built-in voltage independent of manganites, despite the great resistivity change of the manganites and the metal-to-insulator transition above 350 K ( for La0.67Sr0.33MnO3) and similar to 87K ( for La0.29Pr0.38Ca0.33MnO3). In contrast, the increase in the Nb content causes a reduction of the built-in voltage by similar to 0.2 eV. The presence of the depletion layer insensitive to the phase transition of the manganites is believed to be responsible for the present observations.

We present a manganite–titanate junction composed of a 5 nm La0.67Sr0.33MnO3 film and a 1 wt% Nb-doped SrTiO3 substrate, which exhibits a considerable magnetic field effect. The magnetoresistance (MR = (RH − R0)/R0) of the junction is weak in the forward direction but large in the reverse direction. At 300 K, a 5 T magnetic field can lead to a MR larger than −15%. Under a 5 T field, the MR at −1 V is no less than −10% in a wide temperature range from 10 to 310 K. As a comparison, the MR in the junction based on the 150 nm La0.67Sr0.33MnO3 film is weak and the MR in the junction based on the 2 nm La0.67Sr0.33MnO3 film is large only at relatively low temperatures. These results provide a unique possibility of fabricating junctions with large room-temperature MR by tuning the thickness of the manganite film.