Sr₂FeO₃ with Stacked Infinite Chains of FeO₄ Square Planes

The synthesis of Sr₂FeO₃ through a hydride reduction of the Ruddlesden–Popper layered perovskite Sr₂FeO₄ is reported. Rietveld refinements using synchrotron and neutron powder diffraction data revealed that the structure contains corner-shared FeO₄ square-planar chains running along the [010] axis, being isostructural with Sr₂CuO₃ (Immm space group). Fairly strong Fe–O–Fe and Fe–Fe interactions along [010] and [100], respectively, make it an S = 2 quasi two-dimensional (2D) rectangular lattice antiferromagnet. This compound represents the end-member (n = 1) of the serial system Sr_n+1Fe_nO_2n+1, together with previously reported Sr₃Fe₂O₅ (n = 2) and SrFeO₂ (n = ∞), thus giving an opportunity to study the 2D-to-3D dimensional crossover. Neutron diffraction and Mössbauer spectroscopy show the occurrence of G-type antiferromagnetic order below 179 K, which is, because of dimensional reduction, significantly lower than those of the other members, 296 K in Sr₃Fe₂O₅ and 468 K in SrFeO₂. However, the temperature dependence of magnetic moment shows a universal behavior.