Evolution of magnetic structure in Fe4O5

High pressure can stabilize crystal structures unthinkable at ambient conditions with novel and unusual physical properties. The high-pressure research on the Fe-O system during the last decade revealed a whole new family of iron oxides with unusual stoichiometry like Fe4O5, Fe5O6, Fe7O9, etc. They belong to the same homologous series and are comprised of two principal building blocks, the two-dimensional slabs of iron octahedra separated by one-dimensional chains of iron ions coordinated by trigonal prisms. In our recent work, we developed a unified crystallographic approach to this series of iron oxides. Based on this approach we were able to demonstrate that magnetic interactions in the one- dimensional chains have symmetry protection against perturbations from surroundings and that these oxides can adopt either ferromagnetic or antiferromagnetic ground state depending on the width of the octahedral slabs in the structure. In this proposal, we intend to experimentally test these crystallographic conjectures using powder neutron diffraction on the WISH instrument to determine the evolution of magnetic structure in Fe4O5.