Double perovskite Sr2FeMoO6 films : Growth, structure, and magnetic behavior

The structural and magnetic properties of Sr2FeMoO6 thin films prepared by pulsed laser deposition were studied as a function of the laser energy density used to ablate a noncommercial stoichiometric target. Films deposited at a laser fluence as low as 1.6J∕cm2 exhibit a high degree of double perovskite lattice ordering, a ferromagnetic-paramagnetic transition around 355K, and a saturation magnetization of ∼3.4μB∕f.u. On the contrary, films deposited at φ values >3J∕cm2 show a vertically elongated lattice unit cell and the lack of long range ferromagnetic order with a severe decrease of the saturation magnetization (Ms∼1μB∕f.u.). The structural and magnetic properties observed in the latter samples are attributed to lattice disorder and to secondary phases resulting from the ablation process performed at high laser energy density. In these samples the presence of Fe ions not arranged in the Sr2FeMoO6 is confirmed by x-ray absorption measurement at the Fe L2,3 edge.