LaMnO3 Thin Films Grown by Using Pulsed Laser Deposition and Their Simple Recovery to a Stoichiometric Phase by Annealing

We systematically investigated various physical properties of epitaxial LaMnO3 thin films fabricated on SrTiO3 substrate by using pulsed laser deposition. In particular, we observed drastic changes in their properties when the as-grown films were annealed in a reduced-oxygen atmosphere. Whereas the as-grown LaMno(3) film showed ferromagnetic and semiconducting properties with a small optical band gap, the LaMnO3 films annealed at temperature higher than 700 degrees C showed antiferromagnetic and insulating properties with an enlarged band gap. The optical features also changed drastically, in that the optical transition peak shifted to a higher energy with additional fine structures. Such changes were made in a direction such that the LaMno(3) films were more stoichiometric, indicating that the stoichiometric phase could be recovered by simple annealing of the pulsed-laser-deposited films. Finally, possibilities of the polar catastrophe scenario at the interface between LaMnO3 and SrTiO3 are briefly discussed.