Strain-Engineered Ferromagnetism in LaMnO3 Thin Films

A systematic study of the growth process of LaMnO 3 (LMO) thin films, by pulsed laser deposition, on top of SrTiO 3 substrates under different oxygen partial pressures ( P O 2 ) is reported. It is found that the accommodation of the orthorhombic LMO phase onto the cubic STO structure, i.e., the amount of structural strain, is controlled by the background oxygen pressure. We demonstrate that magnetic behavior can be continuously tuned from robust ferromagnetic (FM) ordering to an antiferromagnet. These results strongly point to a strain-induced selective orbital occupancy as the origin of the observed FM behavior, in agreement with recent theoretical calculations.