Room temperature, low temperature and polarized neutron studies of YSr2Fe3O8

The nuclear and magnetic structures of YSr2 Fe-3 O-8 have been studied by using X-ray and neutron powder diffraction. Neutron diffraction data have been collected at room temperature (300 K) and low temperature(12 K). The tetragonal space group P4/mmm was used for nuclear refinements and the orthorhombic space group I(c)mm'm was used for magnetic refinements. All possible oxygen sites in the unit cell are found to be fully occupied resulting in an oxygen occupancy of similar to 8.00 per formula unit. The magnetic structure is based on a unit cell related to the nuclear cell by the transformation of matrix (1 (1) over bar 0/1 1 0/0 0 2). The magnetic origin of the extra peaks, found in the diffraction patterns, was confirmed by polarization analysis method. The iron moments are coupled antiferromagnetically within each FeO2-layer, as well as along the c-axis. The magnetic moments are found to be 3.45(2) mu(B) and 3.54(3) mu(B) at 300 and 12 K, respectively. (C) 2000 Elsevier Science B.V. All rights reserved.