We have, studied the dependence of the resistivity and magnetoresistance (MR) of epitaxial (0 0 1) La0.7Sr0.3MnO3-δ/(0 0 1) LaAlO3 films on controlled vacuum annealing. First, La0.7Sr0.3MnO3-δ films grown by sol-gel process were annealed at O2 (1 atm. oxygen)/1170 K/1 h (we call this as-prepared films); subsequently, these as-prepared films were annealed in vacuum (∼10-6 torr/2 h) at different temperatures, i.e. 720 K, 770 K, 820 K, 920 K, to systematically reduce the oxygen stoichiometry. The resistivity increases systematically with increasing annealing temperature in accord with oxygen content variation. The resistivity shows a metallic behavior (as-prepared films), metal-insulator transitions (films annealed at 720 K, 770 K) and an insulating behavior (films annealed at 820 K, 920 K). Significant MR is observed predominantly near the resistivity peak for the metallic films and at low temperature for the insulating films. These observations demonstrate that the oxygen content, the resistivity and MR behavior of manganese oxides are precisely controllable via vacuum annealing.
Bibliographical noteFunding Information:
Acknowledgements-We thank Dr A.R. Modak for the preparation of the stock solution of La0,7Sro,3Mn03_8 and B.J. Ether for the measurement of the oxygen content by EDXS. This work was supported by the Director, Office of Energy Research, Office of Basic Energy Sciences, Materials Sciences Division of the U.S. Department of Energy under contract No. DE-AC03-76SFOOO98.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Materials Chemistry