Crystal and magnetic structures of Sr2Fe2O5 at elevated temperature

The evolution of crystal and magnetic structures of Sr2Fe2O5 with temperatu re was studied using neutron powder diffraction. The measurements were made in the temperature range from room temperature up to 1223.15 K and the pat terns were analyzed using the Rietveld method. The oxide undergoes two phas e transitions: (i) from the antiferromagnetic to the paramagnetic state and (ii) from the orthorhombic to the cubic structure. We discuss the changes of structural parameters with temperature and propose a new structural mode l for the cubic phase. The diffraction patterns were refined using Ib'm'2, Ibm2, and Fm3c symmetry groups in the antiferromagnetic, the paramagnetic a nd the cubic state, respectively, with Z = 4. (C) 2001 Academic Press.