Mechanism of the Verwey transition in magnetite: Jahn–Teller distortion and charge ordering patterns

We have performed density functional calculations with on-site Coulomb repulsion corrections of systems that may be involved in the Verwey transition in magnetite (Fe(3)O(4)). We find that the lowest energy solution for the minority spin wavefunction in the cubic cell involves orbitally ordered Fe-d and O-p states, which breaks cubic symmetry. This leads to partial charge ordering that triggers a Jahn-Teller distortion and band-gap opening. Our results show this to be the essential mechanism of the Verwey transition. Applying ionic relaxation within a larger tetragonal cell, three patterns of charge ordering are compared and a Pmca pattern matching x-ray data is found to be the most stable.