Thin films of the double perovskite ferromagnet ${\text{Sr}}_2{\text{FeMoO}}_6$ have been grown on MgO(001) substrates by pulsed laser deposition at temperatures as low as $600°\text{C}$. High-resolution X-ray diffraction studies revealed that the deposited films are single-phase ${\text{Sr}}_2{\text{FeMoO}}_6$ epitaxially grown on the MgO substrate. The film grown at $800°\text{C}$ was post-annealed in oxygen producing epitaxial films of ${\text{SrMoO}}_4$ on top of the ${\text{Sr}}_2{\text{FeMoO}}_6$ film. The corresponding magnetization data showed that the post-annealing treatment lowered the saturation magnetic moment from $3.4{\mu }_B$ per formula unit (or /f.u.) for the as-grown ${\text{Sr}}_2{\text{FeMoO}}_6$ film to $1.4{\mu }_B/\text{f}\text{.u}\text{.}$ after annealing. X-ray photoemission measurements as a function of sputtering time further revealed the presence of ${\text{SrMoO}}_4$ on both the as-grown and annealed films and their corresponding depth profiles indicated a thicker ${\text{SrMoO}}_4$ overlayer on the annealed film. The intensity ratios of the $3d$ features of ${\text{Mo}}^{4+}$, ${\text{Mo}}^{5+}$, and ${\text{Mo}}^{6+}$ for ${\text{Sr}}_2{\text{FeMoO}}_6$ remained unchanged with sputtering depth (after 160 s of sputtering) strongly suggesting that the observed secondary phase $\left({\text{SrMoO}}_4\right)$ was formed predominantly on the surface and not in the subgrain boundaries of the as-grown ${\text{Sr}}_2{\text{FeMoO}}_6$ film. The presence of the secondary phase on the surface of the as-grown ${\text{Sr}}_2{\text{FeMoO}}_6$ film therefore plays a major role in contributing to the observed lower value for the saturation magnetic moment than the theoretical value.

• Received 16 December 2008

DOI:https://doi.org/10.1103/PhysRevB.79.174427