Controlling the magnetic properties of LaMnO₃thin films on SrTiO₃(100) by deposition in a O₂/Ar gas mixture

The magnetic, structural, and transport properties of pulsed-laser deposited LaMnO(3) thin films are analyzed as a function of the O(2) partial pressure in the growth environment (using an O(2)/Ar gas mixture). Interestingly, the magnetic properties do not change gradually as the O(2) content increases. Instead, ferromagnetism emerges rapidly with the oxygen; a critical amount of Ar is needed to suppress ferromagnetism effectively in LaMnO(3) thin films. The most dramatic suppression of ferromagnetism occurs only in the narrow window below 10% oxygen, where the ferromagnetic moments decrease by a factor of 17. Above a certain oxygen concentration, the ferromagnetic moment no longer increases with oxygen. The sample grown in pure oxygen shows a metal-insulator transition at ∼200 K, but exhibits an insulating behavior again below ∼150 K. This intermediate metallic behavior is significantly suppressed by using the O(2)/Ar gas mixture.