Neutron diffraction study of the antiferromagnetic oxyhalides Sr3Fe2O5Cl2, Sr3Fe2O5Br2 and Sr3FeCoO5Cl2

The crystal and magnetic structures of the Ruddlesden-Popper related iron oxyhalides, Sr3Fe2O5X2, X = Cl and Br and the mixed B site material Sr3FeCoO5Cl2 have been studied using neutron powder diffraction. The materials consist of double layers of Fe(CO)O-5 square pyramids separated along the z-direction by SrX rocksalt layers. Neutron powder diffraction data were collected at room temperature and 2 K for Sr3Fe2O5Br2 and Sr3FeCoO5Cl2, whilst the thermal dependence of both the nuclear structure and the long range magnetic order of Sr3Fe2O5Cl2 in the range 17 K < T < 625 K has been studied, allowing the materials T-Neel = 590 K to be determined. All three phases adopt G-type antiferromagnetic spin structures, with the moments confined within the xy-plane. The materials possess low temperature moments mu = 4.40(4)mu(B), mu = 4.07(6)mu(B) and mu = 2.11(4)mu(B) for Sr3Fe2O5Cl2, Sr3Fe2O5Br2 and Sr3FeCoO5Cl2, respectively, indicating the presence of high spin iron (111) in all compounds. (C) 2004 Elsevier SAS. All rights reserved.