Controlling the magnetic properties of LaMnO3 thin films on SrTiO3(100) by deposition in a O2/Ar gas mixture

The magnetic, structural, and transport properties of pulsed-laser deposited LaMnO3 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 LaMnO3 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 similar to 200 K, but exhibits an insulating behavior again below similar to 150 K. This intermediate metallic behavior is significantly suppressed by using the O-2/Ar gas mixture.