Crystal and Magnetic Structures of Sr_2Fe_2O_5 at Elevated Temperature

摘要

The evolution of crystal and magnetic structures of Sr_2Fe_2O_5 with temperarture was studied using neutron powder diffraction. The measurements were made in the temperature range from room temperature up to 1223.15 K and the patterns were analyzed using the Rietveld method. The oxide undergoes two phase 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 model for ht ecubic phase. The diffraction patterns were refined using Ib'm'2, Ibm2, and Fm3c symmetry groups in the antiferromagnetic, the paramagnetic and the cubic state,respectively, with Z=4.