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 u sing X-ray and neutron powder diffraction. Neutron diffraction data have be en collected at room temperature (300 K) and low temperature(12 K). The tet ragonal space group P4/mmm was used for nuclear refinements and the orthorh ombic 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 a n oxygen occupancy of similar to 8.00 per formula unit. The magnetic struct ure is based on a unit cell related to the nuclear cell by the transformati on of matrix (1 (1) over bar 0/1 1 0/0 0 2). The magnetic origin of the ext ra 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 foun d 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.