Magnetic structure of Sr2Fe2O5 brownmillerite by single-crystal Mössbauer spectroscopy

• Single-crystal Mössbauer spectroscopy is used to study magnetic structure of Sr2Fe2O5.
• Complete Hamiltonian for hyperfine interactions in excited and ground states was solved.
• Fe3+ magnetic moments are parallel to the shortest crystallographic axis c.
• The orientation of nuclear electric field gradient is similar to that in Ca2Fe2O5.

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 Mössbauer 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 57Fe 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.

Mössbauer spectra of powdered and oriented single-crystal Sr2Fe2O5, analyzed by solving the complete Hamiltonian for hyperfine interactions in the excited and ground states of the 57Fe nuclei, show that the magnetic moments of both octahedrally and tetrahedrally coordinated iron cations are parallel to the shortest c-axis of the orthorhombic brownmillerite unit cell .Figure optionsDownload as PowerPoint slide