Crystal structure and magnetic properties of double perovskite Sr2FeReO6 ceramics synthesized by a combined molten-salt synthesis and solid-state reaction method

Sr2FeReO6 (SFRO) double perovskite ceramics were synthesized by a combined molten-salt synthesis and solid-state reaction (SSR) method under N2 (sample A) and Ar (sample B), and also by direct SSR method under Ar (sample C). All the SFRO ceramics crystallized in a tetragonal structure with I4/m space group. Superstructural reflections such as (011) peak appeared in A-B samples but absent in sample C. Their average crystallite sizes were ∼ 50 nm, and the compositions of the three samples were determined as Sr2Fe1+xRe1−xO6 (x = 0.197, 0.142, and 0.087). XPS spectra revealed that Re existed in dual valence states in sample B, but the dual oxide states of Re and Fe in sample C. Oxygen existed as lattice oxygen in B–C samples. Ferromagnetic behavior was observed in the A-C samples at 2 K and 300 K, and their saturation magnetizations at 2 K were 1.259, 1.477, and 0.842 μB/f.u., respectively.