A two-stage model of Verwey transition in Fe₃O₄: first-principles studies

Fe₃O₄ undergoes a first-order metal-insulator transition, i.e., the Verwey transition at about 120 K. Despite extensive investigations focusing on the Verwey transition, the exact underlying mechanism, particularly the evolution of the electronic structure during the transition, remains debated. In this study, the lattice distortion near the Verwey transition is divided into several intermediate steps. The corresponding electronic structures and magnetic properties at each step are investigated via first-principles calculations. The results reveal that the Verwey transition can be regarded as a two-step phase transition containing a dynamic and a static trimeron network mode. Under the dynamic regime, the charge ordering pattern changes with lattice distortion. Upon further distortion, the system enters the static mode. Additionally, the variations of ferroelectricity and magnetic anisotropy with lattice distortion are investigated. The detailed calculation results may provide insights into the underlying physics of the Verwey transition and promote the understanding of the three-Fe-site trimeron unit.