Quantum State Model of the Verwey Transition in Magnetite

✍ Scribed by H. Kloor; J.M. Honig

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 206 KB
• Volume: 148
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1999.8398

✦ Synopsis

Previous analyses of the Verwey transition in magnetite have been placed on a 5rm footing by a consistent analysis of the statistical properties of an array of quantum states associated with ferrous or ferric ions in octahedrally coordinated interstices of the spinel lattice. This collection is represented by an assembly of bonds and sites. Individual sites can be in one of three con5gurations: empty, as in the Fe 3؉ state, trapped, or polaronic if in the Fe 2؉ state. On neglect of high-energy states involving electron occupation of neighboring lattice sites, one arrives at an analytic equation of state for the order parameter in its dependence on temperature, which can be solved numerically. This equation is su7ciently 6exible to handle both the 5rst-and second-order transitions by appropriate changes in parameters. The present theory rationalizes the experimentally observed changes in the order of the Verwey transition that result from alterations in the sample stoichiometry.