click on figure for more details (Fig.1)
click on figure for more details (Fig.1)
Magnetic structure from high resolution diffraction of ilvaite on D1A
The Fe++ and Fe+++ ordering on the A-sites can be clearly demonstrated. It has been shown that below 116K the Fe++ and Fe+++ spins on the A-sites along one infinite c-axis chain are parallel, and antiparallel to those along the adjoined edge sharing centro-symmetrically related site. Below 40K this order is maintained, but the Fe++ spins on the B-sites order antiferromagnetically as well.
A similar pattern of ferromagnetic ordering within chains, plus antiferromagnetic ordering between chains has been obtained for orthoferrosilite Fe2Si2O6 (Fig.2).
click on figure for more details (Fig.2)
Ferromagnetic ordering within chains plus antiferromagnetic ordering between claims in orthoferrosilite..
Precise D1A powder measurements of the low temperature monoclinic structure of magnetite Fe3O4 have clearly shown the monoclinic splitting at the Verwey transition (Fig. 3.a) and the weak superlattice lines due to the ordering of Fe++ and Fe+++ (Fig. 3.b).
click on figure for more details (Fig.3)
Powder measurements of the low temperature monoclinic structure of magnetite. (a) monoclinic splitting at the Verwey transition, b weak superlattice lines due to the ordering of Fe++ and Fe+++.
Valence charge calculations from precise Fe-O bond lengths obtained by profile refinement have identified some of the Fe++ sites, but others, related by a pseudo centre of symmetry, have taken a little longer.