Thickness dependent microstructures and properties of Sr2Fe10/9Mo8/9O6 films grown in N2

Double perovskite Sr2Fe10/9Mo8/9O6 films with different thicknesses have been prepared on (111)-SrTiO3 substrates by pulsed laser deposition in flowing N2 atmosphere. The X-ray diffraction indicates the films have no impurity phases and are (111) oriented. The epitaxy and local Fe/Mo ordering are confirmed by high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED). Mixed valence states of interior Fe and Mo cations are observed by the x-ray photoelectron spectroscopy. Interestingly, the films show significantly thickness-dependent magnetization properties: at 10 K, the films show the saturated magnetization of 2.30 μB/f.u. (formula unit), 1.12 μB/f.u., and 0.50 μB/f.u., respectively. On the other hand, the thickest film shows a magnetoresistance of −13% at 120 K whereas other two samples show considerably higher resistivity and neglectable MR. The thickness effects on microstructure and properties have been discussed in detail.