Crystallographic and Magnetic Properties of Double Perovskite Oxide Ba_2−xSr_xFeMoO₆

In order to study on the change of magnetic properties according to the tolerance factor, polycrystalline single phase double perovskite oxide Ba_2−x;Sr_xFeMoO₆ (x = 0.0, 0.5, 1.0, 1.5, 2.0) are prepared. The crystallographic and magnetic properties have been studied by X-ray diffraction, magnetization measurements and Mössbauer spectroscopy. The Ba₂FeMoO₆ is analyzed as a cubic structure with Fe³⁺ and Mo⁵⁺ ions ordered at the B-sites. As the x value increases from the cubic structure, the lattice constant decreases more rapidly in the a-b-axis direction than in the c-axis. So that the tetragonal structure starts from x = 1.0. The Curie temperature of the Ba₂FeMoO₆ and Sr₂FeMoO₆ were 345 K and 425 K, respectively. As the value of x increases, the Curie temperature increases linearly. In addition, the magnetic hyperfine field fluctuation due to relaxation effects are observed in the Mössbauer spectrum of all series samples.