Site-selective doping of ordered charge states in magnetite

We report the effect of iron off-stoichiometry in magnetite (Fe3-xO4) on the charge-ordering (Verwey) transition, and the underlying changes in crystal structure. Our detailed analysis reveals that oxidation from Fe2+ to Fe3+ preferentially occurs at one crystallographic site, while the rest of the charge-ordered structure remains intact. This new 'charge order within a charge order' phenomenom is driven by the unusual electronic trimeron distribution around the special site, causing a locally distinct ionisation potential.

Diagram showing anomalous atom position with its excess distortion and location within the crystal lattice.

E. Pachoud, J. Cumby, G. Perversi, J. P. Wright and J. P. Attfield, Site-selective doping of ordered charge states in magnetite, Nature Communications, 11, 2020, 1671.