ON THE CRYSTAL AND HYPERFINE PARAMETERS OF THE HEXAGONAL Ba Cax Sr1_xFe4 O8 MONOFERRITES

Abstract

The alkaline earth monoferrites BaCaxSr1-xFe4O8 with X = 0,0.5and 1, were studied by Mossbauer spectroscopy and neutron diffractometry over a wide range of temperatures (78 - 900 K). The lattice constants were obtained from X-ray powder patterns. The nuclear intensities of coherent Bragg reflections above the magnetic transition temperatures were successfully interpreted according to the space group P31m with one formula unit per unit cell. Neutron magnetic intensities and magnetically split Mossbauer spectra showed that all compositions to be antiferro-magnetic due to interactions between nearest neighbour Fe3" ions with magnetic unit cell has the same periodicity as the crystallographic one. The reduced hyperfine magnetic fields of the Fet ions were found to follow the Briliouin curve for S = 5/2. Crystallographic and Mossbauer parameters were reported and relationships between structural and magnetic properties were discussed