On the Verwey Transition in Magnetite

Abstract
The Verwey transition in magnetite is investigated using a band model with interatomic Coulomb energy introduced by Cullen and Callen. This model is treated in the Hartree‐Fock approximation. A tight‐binding calculation of the band structure with Verwey ordering yields a gap in the single‐particle excitation spectrum for M = (U/2|h|) m > 1 (U Coulomb energy, h overlap integral, m ordering parameter). Below the Verwey temperature Tv semiconducting behaviour for M > 1 and a region of gapless Verwey ordering and semimetallic behaviour for 0 < M ⩽ 1 is found.