Magnetic structure of Sr2Fe2O5 brownmillerite by single-crystal Mossbauer spectroscopy

Abstract

In order to determine orientation of the Fe3+ magnetic moments and electric field gradient (efg) axes in the brownmillerite-type strontium ferrite structure for both iron sublattices where the efg tensor is not axially symmetric, the Mossbauer spectra of powdered and oriented single-crystal Sr2Fe2O5 were analyzed by solving the complete Hamiltonian for hyperfine interactions in the excited and ground states of the Fe-57 nuclei. The magnetic moments of both octahedrally and tetrahedrally coordinated iron cations lie on the ac-plane of the orthorhombic unit cell and are parallel to the shortest c-axis, whilst the main efg axes are parallel to the longest crystallographic axis, b. This orientation is similar to that in Ca2Fe2O5, in spite of the structural differences of strontium and calcium ferrite brownmillerites at low temperatures. (c) 2013 Elsevier Inc. All rights reserved.