Editing Iron(II,III) oxide (section)

== Structure ==
Fe<sub>3</sub>O<sub>4</sub> has a cubic inverse [[spinel group]] structure which consists of a cubic close packed array of oxide ions where all of the Fe<sup>2+</sup> ions occupy half of the octahedral sites and the Fe<sup>3+</sup> are split evenly across the remaining octahedral sites and the tetrahedral sites.

Both [[iron(II) oxide|FeO]] and [[iron(III) oxide|γ-Fe<sub>2</sub>O<sub>3</sub>]] have a similar cubic close packed array of oxide ions and this accounts for the ready interchangeability between the three compounds on oxidation and reduction as these reactions entail a relatively small change to the overall structure.<ref name="Greenwood"/> Fe<sub>3</sub>O<sub>4</sub> samples can be [[non-stoichiometric]].<ref name="Greenwood"/>

The [[ferrimagnetism]] of Fe<sub>3</sub>O<sub>4</sub> arises because the electron spins of the Fe<sup>II</sup> and Fe<sup>III</sup> ions in the octahedral sites are coupled and the spins of the Fe<sup>III</sup> ions in the tetrahedral sites are coupled but anti-parallel to the former. The net effect is that the magnetic contributions of both sets are not balanced and there is a permanent magnetism.<ref name = "Greenwood"/>

In the molten state, experimentally constrained models show that the iron ions are coordinated to 5 oxygen ions on average.<ref name="ShiFeOx2020">{{cite journal | vauthors = Shi C, Alderman OL, Tamalonis A, Weber R, You J, Benmore CJ |title=Redox-structure dependence of molten iron oxides |journal=Communications Materials |date=2020 |volume=1 |issue=1 |page=80 |doi=10.1038/s43246-020-00080-4 |bibcode=2020CoMat...1...80S |s2cid=226248368 |ref=ShiFeOx2020|doi-access=free }}</ref>  There is a distribution of coordination sites in the liquid state, with the majority of both Fe<sup>II</sup> and Fe<sup>III</sup> being 5-coordinated to oxygen and minority populations of both 4- and 6-fold coordinated iron.