The crystal and magnetic structures of Sr₂CoFeO₅

The crystal and magnetic structures of the brownmillerite Sr₂CoFeO₅ have been refined from neutron powder diffraction data collected at room temperature, space group Icmm, a = 5.6243(2), b = 15.6515(5), c = 5.5017(2) Å. The transition metal ions are partially ordered over the 6- and 4-coordinate cation sites; in addition the 4-coordinate sites themselves have a positional disorder. The compound shows G-type antiferromagnetic order at room temperature with ordered magnetic moments of 3.2 and 2.9 μ_B, aligned along z, at the 6- and 4-coordinate sites, respectively. The low magnitude of the ordered moments is discussed.