Zener double exchange from local valence fluctuations in magnetite

TitleZener double exchange from local valence fluctuations in magnetite
Publication TypeJournal Article
Year of Publication2007
AuthorsMcQueeney RJ, Yethiraj M, Chang S, Montfrooij W, Perring TG, Honig JM, Metcalf P
Journal TitlePhysical Review Letters
Date PublishedDec
Type of ArticleArticle
ISBN Number0031-9007
Accession NumberISI:000251674300040

Magnetite (Fe3O4) is a mixed valent system where electronic conductivity occurs on the B site (octahedral) iron sublattice of the spinel structure. Below T-V=123 K, a metal-insulator transition occurs which is argued to arise from the charge ordering of 2+ and 3+ iron valences on the B sites (Verwey transition). Inelastic neutron scattering measurements show that optical spin waves propagating on the B site sublattice (similar to 80 meV) are shifted upwards in energy above T-V due to the occurrence of B-B ferromagnetic double exchange in the mixed valent phase. The double exchange interaction affects only spin waves of Delta(5) symmetry, not all modes, indicating that valence fluctuations are slow and the double exchange is constrained by short-range electron correlations above T-V.

Alternate JournalPhys. Rev. Lett.