Structural and magnetic behavior of the cubic oxyfluoride SrFeO2F studied by neutron diffraction

The oxyfluoride SrFeO2F has been prepared via a low temperature route involving the infinite-layer SrFeO2 and XeF2. SrFeO2F crystallizes in the cubic space group Pm-3m with disordered oxygen and fluorine atoms on the anion site. Recent reports demonstrated that SrFeO2F is antiferromagnetic at room temperature and the zero field cooled and field cooled curves diverge at similar to 150 K and similar to 60 K, suggesting that the material has a spin glassy magnetic state at low temperatures. In this article, variable-temperature neutron diffraction (4-723 K) was performed to clarify the magnetic behavior observed in this material. Neutron powder diffraction measurements confirmed the antiferromagnetic (AFM) ordering of the system at room temperature. Below 710(1) K, the magnetic structure is a G-type AFM structure characterized by a propagation vector k=(1/2, 1/2, 1/2). The ordered moments on Fe3+ are 4.35(6)mu(B) at 4 K and 4.04(5)mu(B) at 290 K. Our results indicate that the cubic structure is retained all the way to base temperature (4 K) in contrast to PbFeO2F. These results are compared with those of Pb and Ba analogs which exhibit very similar magnetic behavior. Furthermore, the observation of magnetic reflections at 4 K in the diffraction pattern shows the absence of the previously proposed spin glassy behavior at low temperatures. Previous proposals to explain the ZFC/FC divergences are examined. (C) 2014 Elsevier Inc. All rights reserved.