Pulsed laser deposition films from a Ba₂FeMoO₆ target onto SrTiO₃[001]: Chemical and magnetic inhomogeneity

Pulsed laser deposition films from Ba₂FeMoO₆ (BFMO) targets onto SrTiO₃[001] (STO) substrates have been reported previously to have non-zero magnetism at 300 K, a majority of magnetic ordering at 240 K that is less than the 370 K ordering temperature of polycrystalline BFMO, and suppressed saturation magnetization compared to polycrystalline BFMO. To interrogate these previously reported observations of BFMO on STO, we have used a combination of x-ray diffraction, atomic force microscopy, x-ray and neutron reflectivity, and x-ray photoelectron spectroscopy that shows inhomogeneities. The present results show off-stoichiometry on the A-site by incorporation of Sr from the substrate and on the B-site to have %Fe/%Mo > 1 by evolution of BaMoO₄. There is an enhanced ordering temperature and magnetic response nearer to the SrTiO₃ interface compared to the air interface. Depth dependent strain and microstructure are needed to explain the magnetic response. Holistic considerations and implications are also discussed.