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

Abstract

We have performed density functional calculations with on-site Coulomb repulsioncorrections of systems that may be involved in the Verwey transition in magnetite(Fe3O4). We find that the lowest energy solution for the minority spin wavefunction in the cubiccell involves orbitally ordered Fe-d and O-p states, which breaks cubic symmetry. This leadsto partial charge ordering that triggers a Jahn–Teller distortion and band-gap opening. Ourresults show this to be the essential mechanism of the Verwey transition. Applying ionicrelaxation within a larger tetragonal cell, three patterns of charge ordering are compared and aPmca pattern matching x-ray data is found to be the most stable.