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 A(2)FeWO(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 Sr2FeWO6 (SFW) compound adopts a monoclinic unit cell (space group P2(1)/n, a = 5.6480(4), b = 5.6088(4), c = 7.9362(6) Angstrom and beta = 89.99(2)), and the Ba2FeWO6 (BFW) compound is tetragonal (space group I4/m, a = 5.7547 (4), c = 8.125 (1) Angstrom). 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 = (01/21/2). The magnetic moment of iron was found to be 3.86(4)mu(B) and 3.49(2)mu(B) at 10 K for the Sr- and the Ba-containing compounds, respectively. (C) 2002 Elsevier Science Ltd. All rights reserved.