A study on the nuclear and magnetic structure of the double perovskites A 2FeWO 6 (A = Sr, Ba) by neutron powder diffraction and reverse Monte Carlo modeling

Abstract

Perovskite-type complex metal oxides A 2FeWO 6 (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 Sr 2FeWO 6 (SFW) compound adopts a monoclinic unit cell (space group P2 1/ n, a=5.6480(4), b=5.6088(4), c=7.9362(6) Å and β=89.99(2)°), and the Ba 2FeWO 6 (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) μ B and 3.49(2) μ B at 10 K for the Sr- and the Ba-containing compounds, respectively.