A study on the nuclear and magnetic structure of the double perovskites A2FeWO6 (A = Sr, Ba) by neutron powder diffraction and reverse Monte Carlo modeling

Perovskite-type complex metal oxides A2FeWO6 (A=Sr, Ba) were prepared by a standard solid state reaction method. Rietveld analysis of neutron powder diffraction (NPD) data at 295 K shows that the Sr2FeWO6 (SFW) compound adopts a monoclinic unit cell (space group P21/n, a=5.6480(4), b=5.6088(4), c=7.9362(6) Å and β=89.99(2)°), and the Ba2FeWO6 (BFW) compound is tetragonal (space group I4/m, a=5.7547(4), c=8.125(1) Å). A combination of a reverse Monte Carlo (RMC) technique and Rietveld analysis shows that the low temperature (10 K) magnetic structures of SFW and BFW are antiferromagnetic based on a unit cell related to that of the nuclear structure by a propagation vector, k=(0 1/2 1/2). The magnetic moment of iron was found to be 3.86(4)μB and 3.49(2)μB at 10 K for the Sr- and the Ba-containing compounds, respectively.