Magnetoresistance in oxygen deficient La0.75Sr0.25MnO3-δ thin films prepared by pulsed laser deposition

High-quality and (0 0 1)-oriented La0.75Sr0.25MnO3-delta thin films are deposited on (0 0 1)SrTiO3 substrates at different oxygen pressures by pulsed laser deposition. Significant effect of the oxygen pressure on the microstructure, the electrical and magnetoresistive (MR) properties of the as-prepared films is demonstrated. C-axis expansion of the films grown at the reduced pressure is identified. While the films deposited at low oxygen pressure show high resistivity and enhanced-MR value, both the peak positions of MR value as a function of temperature and the ferromagnetic transition point shift towards low temperature. The possible mechanism responsible for the oxygen stoichiometric effect is discussed in terms of the point defect model. (C) 1999 Elsevier Science B.V. All rights reserved.