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.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Materials Chemistry