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The effects of vacuum annealing on the structural and transport properties of the La0.67Ca0.33MnO3−δ films grown on SrTiO3 (LCMO/STO) and NdGaO3 (LCMO/NGO) substrates have been studied. A lattice expansion due to oxygen release during the annealing is observed. Under the same condition, the change of the out-of-plane lattice parameter in LCMO/STO is two to three times larger than that in LCMO/NGO, indicating a strong tendency for the oxygen in the former to escape. Correspondingly, the metal-to-semiconductor transition shifts to lower temperatures, linearly with lattice constant until a critical value, Δd=0.03 Å for LCMO/STO and Δd=0.05 Å for LCMO/NGO, after which a sudden drop of the transition temperature to zero occurs. The different lattice strains in both films are presumably responsible for the different critical oxygen contents for the occurrence of the resistive transition.

We report on the observation of enhanced low-field magnetoresistance in La2/3Ca1/3MnO3/Pr2/3Ca1/3MnO3 (LCMO/PCMO) superlattices with ultrathin PCMO layers. In particular, [LCMO(100 Å)/PCMO(10 Å)]17 superlattice exhibits magnetoresistance MR=Δρ/ρ0=−55% in a magnetic field of 500 Oe and at temperature 219 K. The enhancement is associated with the ultrasharp metal–insulator transition.

We report the voltage tunable photodetecting properties of a La0.4Ca0.6MnO3 film grown on miscut LaSrAlO4 (001) substrates under ultraviolet pulsed laser irradiation at ambient temperature. The photovoltage and photocurrent peak sensitivities can be tuned in the range of 0.295–0.786 V/mJ and 0.172–0.314 A/mJ, respectively, when the applied bias is changed from −20 to +20 V, indicating that the vicinal manganite film can be used as an electric tunable ultraviolet photodetector. A possible mechanism based on the high resolution transmission electron microscopy is introduced to explain the experiment results.

The photovoltaic effect (PVE) of a heterojunction composed of a La0.7Ce0.3MnO3 (LCE) film and a 0.5wt.% Nb-doped SrTiO3 crystal has been experimentally studied. A strong PVE was observed, and the maximum photovoltage was ∼54.1mV, when the LCE film was exposed to light with a wavelength (λ) of 460nm and a power of ∼6.5μW. The PVE remains significant up to λ=660nm, though it decreases gradually with the increase of wavelength. Oxygen release of the LCE film depresses the PVE considerably and modifies the rectifying property of the junction. A logarithmic variation of photovoltage with junction resistance was observed. The weakening of the ferromagnetic order of the LCE film due to the incorporation of oxygen vacancies may be the reason for the depression of the PVE.